If your OBD-II scanner displays P0124, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an intermittent signal from the Throttle/Pedal Position Sensor “A” circuit.
The generic OBD-II definition for P0124 is:
Throttle/Pedal Position Sensor/Switch “A” Circuit Intermittent
Unlike P0120, which indicates a general circuit malfunction, P0122, which indicates a low-voltage condition, or P0123, which indicates excessive voltage, P0124 tells the PCM that the sensor signal is dropping out, fluctuating, or becoming unstable intermittently.
In other words, the sensor may operate perfectly one moment and then suddenly produce an unexpected signal before returning to normal.
Intermittent electrical faults are among the most frustrating problems to diagnose because the vehicle often behaves normally while it’s sitting in the repair bay.
Depending on the manufacturer, Sensor “A” may refer to:
- Throttle Position Sensor (TPS) A
- Throttle Position Sensor 1
- Accelerator Pedal Position Sensor A
- Accelerator Pedal Position Sensor 1
- Primary electronic throttle position sensor
- Primary accelerator pedal sensor
- An internal sensor integrated into the electronic throttle body
Because manufacturers use different electronic throttle strategies, P0124 does not always identify the same physical component.
Some vehicles monitor a serviceable throttle position sensor mounted on the throttle shaft.
Others monitor an internal sensor located inside the electronic throttle body.
Many drive-by-wire vehicles use the accelerator pedal assembly itself.
Knowing which component your vehicle calls Sensor “A” is the first step toward an accurate diagnosis.
Replacing the wrong part is an excellent way to make your wallet lighter without making the Check Engine Light disappear.
What Does the P0124 Code Mean?
P0124 indicates that the PCM has detected an intermittent or erratic voltage signal from the primary throttle or accelerator pedal position sensor.
Instead of remaining smooth and predictable, the signal unexpectedly changes, drops out, spikes, or disappears long enough for the PCM to recognize that the circuit is unreliable.
Most throttle-position sensors operate using three primary circuits:
- A regulated 5-volt reference
- A dedicated sensor ground
- A signal wire that reports throttle position
As the throttle plate or accelerator pedal moves, the signal voltage changes smoothly across its operating range.
On many analog systems this commonly ranges between:
- Approximately 0.5 volts at closed throttle
- Approximately 4.5 volts at wide-open throttle
Actual values vary depending on:
- Vehicle manufacturer
- Sensor design
- Electronic throttle strategy
- PCM calibration
- Hall-effect or potentiometer technology
The important factor is not the exact voltage.
The important factor is that the voltage changes smoothly and consistently.
If the PCM detects:
- Sudden voltage spikes
- Unexpected signal dropouts
- Rapid fluctuations
- Missing signal
- Intermittent open circuits
- Signal interruptions caused by vibration
it stores P0124.
Unlike P0122 or P0123, the signal may return to normal immediately after the fault occurs.
P0124 Quick Facts
| Item | Information |
|---|---|
| DTC | P0124 |
| Generic Definition | Throttle/Pedal Position Sensor “A” Circuit Intermittent |
| System | Electronic Throttle Control |
| Severity | Moderate to High |
| Safe to Drive? | Generally No |
| Common Symptoms | Hesitation, intermittent Reduced Engine Power, poor throttle response, surging, Check Engine Light |
| Common Causes | Loose connector, damaged wiring, failing TPS, failing APP sensor, intermittent ground, connector corrosion |
| Typical Repair Cost | $100–$1,200+ |
| Related Codes | P0120, P0121, P0122, P0123, P0224, P2135 |
How the Electronic Throttle System Works
Modern vehicles use Electronic Throttle Control (ETC) instead of a traditional mechanical throttle cable.
When the driver presses the accelerator pedal:
- Accelerator Pedal Position sensors measure pedal movement.
- The PCM calculates the driver’s torque request.
- The PCM commands the electronic throttle motor.
- Throttle Position Sensors verify actual throttle angle.
- The PCM compares requested and actual throttle positions thousands of times every minute.
Because throttle position directly affects:
- Engine torque
- Fuel delivery
- Ignition timing
- Transmission shifting
- Cruise control
- Traction control
- Stability control
the PCM constantly checks that all throttle-related sensors agree with one another.
If one signal suddenly disappears or behaves erratically, the PCM assumes the circuit cannot be trusted.
Why Multiple Position Sensors Are Used
Electronic throttle systems use redundant sensors for safety.
A typical accelerator pedal contains:
- APP Sensor A
- APP Sensor B
A modern electronic throttle body commonly contains:
- TPS Sensor A
- TPS Sensor B
Rather than trusting one sensor alone, the PCM compares both signals continuously.
Depending on manufacturer design:
- Both sensors may increase together.
- One sensor may increase while the other decreases.
- One may operate over a different voltage range.
- One may serve as a verification signal.
The PCM knows exactly how these sensors should relate to one another.
If Sensor “A” suddenly loses its signal, spikes unexpectedly, or fluctuates while Sensor “B” remains stable, the PCM identifies the condition as an intermittent circuit fault and stores P0124.
How a Throttle Position Sensor Works
A throttle-position sensor converts throttle angle into an electrical signal that the PCM can interpret.
Depending on the vehicle, the sensor may use:
- Potentiometer technology
- Hall-effect electronics
- Magnetoresistive sensing
- Integrated digital electronics
Potentiometer Sensors
Older TPS designs use a resistive strip and movable contact.
As the throttle rotates, the contact slides across the resistor.
Wear over time can create:
- Dead spots
- Signal interruptions
- Sudden voltage changes
- Worn tracks
- Intermittent electrical contact
These failures commonly trigger P0124 before progressing into permanent low- or high-voltage faults.
Hall-Effect Sensors
Many newer systems eliminate mechanical contact.
Hall-effect sensors are generally more reliable but can still fail because of:
- Moisture intrusion
- Internal electronic failure
- Connector corrosion
- Wiring damage
- Heat damage
- Electrical interference
Regardless of design, the PCM expects the signal to remain smooth and uninterrupted.
How the Accelerator Pedal Position Sensor Works
On drive-by-wire vehicles, the accelerator pedal itself contains electronic sensors.
Instead of pulling a throttle cable, the pedal reports the driver’s requested acceleration electronically.
The PCM uses this information to control:
- Throttle opening
- Engine torque
- Fuel delivery
- Ignition timing
- Cruise control
- Transmission operation
- Traction control
- Stability control
If the pedal signal intermittently disappears or fluctuates unexpectedly, the PCM can no longer determine the driver’s true request.
Most manufacturers respond by reducing engine power until reliable information returns.
How the PCM Detects P0124
The PCM continuously evaluates Sensor “A” for smooth, predictable operation.
P0124 may be stored when the PCM detects:
- Signal interruptions
- Intermittent voltage loss
- Random voltage spikes
- Signal fluctuations
- Sudden dropouts
- Temporary open circuits
- Intermittent short circuits
- Signal disagreement with Sensor B
- Signal changes inconsistent with throttle movement
Unlike P0122 or P0123, the voltage itself may be perfectly normal before and after the failure.
The problem is that it fails intermittently, making diagnosis considerably more challenging.
What Does “Circuit Intermittent” Mean?
“Circuit Intermittent” means the electrical signal is not consistently reliable.
The PCM occasionally loses confidence in the signal because it behaves unpredictably.
Common causes include:
- Loose electrical connectors
- Broken wiring inside insulation
- Corroded terminals
- Heat-related electrical expansion
- Vibration-sensitive wiring
- Failing throttle-position sensor
- Failing accelerator-pedal sensor
- Poor sensor ground
- Damaged connector locks
- Internal electronic component failure
Unlike a complete circuit failure, intermittent faults often disappear before a technician begins testing.
That’s why P0124 has earned a reputation for testing patience almost as much as it tests electrical systems.
Common P0124 Scan Tool Patterns
Because P0124 is an intermittent fault, live scan data is often the fastest way to identify the source of the problem.
Unlike P0122 or P0123, the sensor may operate perfectly during one drive and fail only briefly during another.
Using a scan tool capable of graphing live sensor data dramatically improves the chances of finding the fault.
Pattern 1: Sensor A Drops Out Briefly
Live data may show:
- Sensor A suddenly dropping to zero
- Immediate recovery
- No corresponding throttle movement
- Sensor B remaining normal
Possible causes include:
- Loose connector
- Broken signal wire
- Failing throttle position sensor
- Failing accelerator pedal sensor
Pattern 2: Signal Suddenly Spikes
Instead of dropping out, the voltage may suddenly jump.
Possible scan-tool readings include:
- 0% to 100%
- 15% to 95%
- Sudden five-volt spike
- Immediate return to normal
Possible causes:
- Connector movement
- Internal sensor failure
- Signal wire shorting intermittently
- Moisture intrusion
Pattern 3: Sensor A Freezes
The signal stops changing even though the throttle continues moving.
Possible causes:
- Internal TPS failure
- Pedal sensor failure
- Wiring fault
- Loose terminal
- PCM connector issue
Pattern 4: Fault Only Appears While Driving
Many P0124 vehicles idle perfectly.
The code only appears during:
- Acceleration
- Braking
- Cornering
- Rough roads
- Highway speeds
- Engine vibration
This strongly suggests an intermittent electrical connection.
Pattern 5: Harness Movement Reproduces the Fault
Moving the engine harness while watching live data may cause:
- Sudden voltage spikes
- Signal loss
- Reduced Engine Power
- Check Engine Light
This often identifies damaged wiring hidden inside the insulation.
Pattern 6: Multiple Throttle Codes
P0124 may appear with:
- P0120
- P0121
- P0122
- P0123
- P0224
- P2135
- P2138
When multiple throttle-related codes appear together, inspect the shared wiring and connectors before replacing components.
Common Symptoms of P0124
Symptoms depend on:
- How frequently the fault occurs
- Vehicle manufacturer
- Electronic throttle strategy
- Whether fail-safe mode activates
Common symptoms include:
- Check Engine Light
- Reduced Engine Power message
- Intermittent limp mode
- Hesitation
- Delayed acceleration
- Engine surging
- Bucking
- Jerking
- High idle
- Rough idle
- Stalling
- Hard starting
- Cruise control disabled
- Stability control warning
- Traction control warning
- Transmission shift concerns
- Poor fuel economy
- Inconsistent throttle response
The vehicle may drive perfectly for several days before the fault suddenly returns.
Check Engine Light
Most vehicles illuminate the Check Engine Light after the PCM detects repeated signal interruptions.
Additional warnings may include:
- Reduced Engine Power
- Electronic Throttle Control
- Service Engine Soon
- Wrench warning
- Stability Control warning
- Traction Control warning
Hesitation During Acceleration
One of the earliest symptoms is hesitation.
Because the PCM briefly loses throttle information, acceleration may feel:
- Delayed
- Inconsistent
- Jerky
- Weak
- Unpredictable
Drivers often describe it as if someone briefly lifted off the accelerator.
Intermittent Reduced Engine Power
Unlike permanent throttle faults, P0124 often causes Reduced Engine Power only while the fault is active.
Once the signal returns, the vehicle may temporarily drive normally again.
This intermittent behavior often confuses owners into believing the problem has fixed itself.
Unfortunately, wiring problems rarely heal overnight.
Engine Surging
An unstable throttle signal can cause repeated throttle corrections.
The PCM continually adjusts engine torque while attempting to determine the true throttle position.
Possible symptoms include:
- Engine surging
- Bucking
- Oscillating RPM
- Uneven acceleration
- Random throttle changes
High or Unstable Idle
Intermittent throttle-position data may affect idle calculations.
Possible symptoms include:
- Idle surging
- High idle
- Slow return to idle
- RPM fluctuations
- Rough idle
Stalling
Some vehicles stall because the PCM briefly loses throttle-position information during idle.
Stalling may occur:
- At traffic lights
- During deceleration
- Immediately after startup
- While shifting into gear
Cruise Control Disabled
Cruise control relies on accurate throttle-position information.
If Sensor “A” becomes unreliable, the PCM typically disables cruise control until repairs are completed.
Transmission Shift Problems
Throttle-position data influences automatic transmission operation.
An intermittent signal may cause:
- Harsh shifts
- Delayed shifts
- Early upshifts
- Late downshifts
- Torque-converter complaints
Transmission symptoms frequently disappear after correcting the throttle fault.
Is P0124 Serious?
Yes.
P0124 should be considered a moderate-to-high severity diagnostic trouble code.
Because the fault directly affects electronic throttle control, drivability can quickly become unpredictable.
Possible consequences include:
- Reduced Engine Power
- Limp mode
- Hesitation
- Stalling
- Poor acceleration
- Cruise control cancellation
- Disabled stability systems
Can You Drive With P0124?
Driving with P0124 is generally not recommended.
A short trip may be possible if:
- Throttle response remains normal
- No Reduced Engine Power message appears
- The vehicle accelerates predictably
Avoid driving if:
- Limp mode activates repeatedly
- The engine stalls
- Acceleration becomes unpredictable
- Multiple throttle-related codes are stored
Intermittent electrical faults rarely become more reliable over time.
P0124 vs Related Codes
Understanding related codes helps narrow the diagnosis.
P0120
General Sensor “A” circuit malfunction.
P0121
Sensor performance or range problem.
P0122
Sensor voltage too low.
P0123
Sensor voltage too high.
P0124
Sensor signal becomes intermittent or unstable.
P0224
Throttle/Pedal Position Sensor “B” Circuit Intermittent.
P2135
Sensor A and Sensor B correlation fault.
P0124 often appears before a sensor completely fails and begins setting P0122 or P0123.
30 Common Causes of P0124
The most common causes include:
- Loose throttle-body connector
- Loose accelerator-pedal connector
- Failing throttle-position sensor
- Failing accelerator-pedal sensor
- Broken signal wire
- Broken ground wire
- Corroded connector terminals
- Moisture intrusion
- Oil contamination
- Damaged connector locks
- Bent connector pins
- Weak terminal tension
- Harness rubbing on engine components
- Heat-damaged wiring
- Rodent-damaged wiring
- Previous poor wiring repairs
- Engine harness movement
- Dashboard wiring damage
- Aftermarket pedal controller
- Remote-start installation
- Alarm-system wiring
- Shared ground problems
- Shared five-volt reference issues
- PCM connector corrosion
- Battery voltage instability
- Charging-system faults
- Electronic throttle-body failure
- Accelerator pedal assembly failure
- PCM software issues
- Internal PCM failure (rare)
Final Thoughts
The P0124 Throttle/Pedal Position Sensor “A” Circuit Intermittent code indicates that the PCM has detected an unstable or unreliable throttle-position signal rather than a permanently high or low voltage.
The most common causes include:
- Loose connectors
- Wiring damage
- Intermittent grounds
- Failing throttle-position sensors
- Accelerator-pedal sensor failures
- Internal electronic throttle-body faults
Unlike many electrical codes, P0124 often disappears before diagnosis begins, making careful live-data analysis and wiring inspection essential.
The next section of this guide walks through complete diagnostic procedures, including:
- Live scan-tool analysis
- Wiggle testing
- Voltage testing
- Five-volt reference testing
- Oscilloscope diagnosis
- Wiring repair
- Connector testing
- Throttle-body testing
- Accelerator-pedal testing
- Repair procedures
- Relearn procedures
- Repair costs
- Manufacturer-specific diagnostics
- Final repair verification
Following a systematic diagnostic process helps identify the true intermittent fault before it becomes a permanent one.
How to Diagnose the P0124 Code
Diagnosing P0124 is different from diagnosing P0122 or P0123 because the signal is intermittent rather than consistently high or low.
The throttle or pedal position sensor may operate perfectly while the vehicle is parked, only to fail briefly when:
- The engine vibrates
- The harness moves
- The vehicle hits a bump
- Moisture enters a connector
- Components warm up
- Electrical resistance changes
Finding an intermittent fault requires patience, live data, and a systematic testing process.
The code may involve:
- Throttle Position Sensor (TPS)
- Accelerator Pedal Position (APP) Sensor
- Electronic throttle body
- Accelerator pedal assembly
- Wiring harness
- Connector terminals
- Five-volt reference circuit
- Sensor ground
- PCM connector
- PCM software
Always verify what the manufacturer identifies as Sensor “A” before replacing components.
P0124 Safety Precautions
Electronic throttle systems can activate unexpectedly.
Before testing:
- Park on a level surface.
- Apply the parking brake.
- Shift into Park or Neutral.
- Keep hands clear of the throttle plate.
- Disconnect the battery before wiring repairs unless live testing is required.
- Use approved back-probe leads.
- Never apply battery voltage directly to sensor circuits.
- Support battery voltage with a maintainer during extended testing.
The throttle plate may move automatically whenever the ignition is switched on.
Tools Needed
A thorough P0124 diagnosis may require:
- Professional scan tool
- Live-data graphing
- Oscilloscope
- Digital multimeter
- Back-probe leads
- Wiring diagrams
- Factory service information
- Terminal test kit
- Battery maintainer
- Electrical contact cleaner
- Basic hand tools
An intermittent code often requires more than a simple code reader.
Step 1 – Confirm the Code
Connect the scan tool and record:
- Stored DTCs
- Pending DTCs
- Permanent DTCs
- Freeze-frame data
- Battery voltage
- Engine RPM
- Vehicle speed
- Engine load
- TPS A
- TPS B
- APP A
- APP B
- Commanded throttle angle
- Actual throttle angle
Do not erase the code until all freeze-frame information has been saved.
Freeze-frame data frequently reveals the conditions under which the fault occurred.
Step 2 – Check for Related Codes
P0124 often appears with:
- P0120
- P0121
- P0122
- P0123
- P0220
- P0221
- P0222
- P0223
- P0224
- P0638
- P2100
- P2101
- P2111
- P2112
- P2120
- P2135
- P2138
Related codes help determine whether the fault affects:
- One sensor
- Multiple sensors
- Shared wiring
- Electronic throttle operation
| Code Combination | Likely Cause |
|---|---|
| P0124 only | Sensor A intermittently failing |
| P0124 + P2135 | Sensor disagreement |
| P0124 + P0224 | Wiring or shared circuit |
| Multiple throttle codes | Harness or connector problem |
| P0124 + throttle actuator codes | Electronic throttle body |
Step 3 – Verify Sensor “A”
Consult factory service information.
Determine:
- Sensor location
- Connector pinout
- Five-volt reference
- Sensor ground
- Signal wire
- Expected voltage
- Sensor relationship to Sensor B
Different manufacturers assign Sensor “A” differently.
Never assume the code always points to the throttle body.
Step 4 – Check Battery and Charging Voltage
Electronic throttle systems require stable voltage.
Typical readings:
Engine OFF:
- Approximately 12.6 volts
Engine RUNNING:
- Approximately 13.5–14.8 volts
Inspect:
- Battery terminals
- Ground straps
- Charging voltage
- Alternator output
Voltage instability may contribute to intermittent electronic throttle faults.
Step 5 – Perform a Complete Visual Inspection
Inspect:
- Throttle-body connector
- Accelerator-pedal connector
- Engine harness
- Firewall harness
- PCM connector
- Ground points
- Harness routing
Look for:
- Chafed wiring
- Loose connectors
- Bent pins
- Corrosion
- Moisture
- Oil contamination
- Broken connector locks
- Previous repairs
- Heat damage
Many intermittent faults are visible before electrical testing begins.
Step 6 – Inspect the Throttle Body Connector
Disconnect the connector.
Inspect:
- Terminal condition
- Corrosion
- Moisture
- Heat damage
- Bent terminals
- Loose locking tabs
- Broken seals
A connector that appears secure may still contain one loose terminal.
Step 7 – Inspect the Accelerator Pedal Connector
If the vehicle uses the pedal as Sensor “A”, inspect:
- Pedal connector
- Interior harness
- Carpet interference
- Moisture intrusion
- Remote-start wiring
- Alarm wiring
- Aftermarket pedal controllers
Many intermittent pedal faults originate beneath the dashboard.
Step 8 – Observe Live Data
Turn the ignition ON.
Monitor:
- TPS A
- TPS B
- APP A
- APP B
- Commanded throttle angle
- Actual throttle angle
Healthy signals should move smoothly with no sudden interruptions.
A brief spike or dropout is enough to trigger P0124.
Step 9 – Graph Sensor Data
Graphing is considerably more useful than watching changing numbers.
Look for:
- Sudden spikes
- Dropouts
- Flat spots
- Signal interruptions
- Inconsistent movement
Intermittent failures are often obvious on a graph.
Step 10 – Slowly Sweep the Accelerator
Slowly depress the accelerator pedal several times.
Repeat:
- Slowly
- Moderately
- Quickly
Watch for:
- Signal interruptions
- Sudden jumps
- Flat spots
- Sensor disagreement
Repeat the test several times.
Intermittent failures rarely occur on command.
Step 11 – Compare Sensor A With Sensor B
Modern electronic throttle systems constantly compare redundant sensors.
Possible observations:
Sensor A Drops Out
Sensor B remains normal.
Possible causes:
- Failing sensor
- Wiring fault
- Loose connector
Both Sensors Drop Out
Possible causes:
- Shared ground
- Shared reference
- PCM connector
- Power supply
Pedal Stable — Throttle Drops Out
Likely throttle body issue.
Throttle Stable — Pedal Drops Out
Likely pedal assembly issue.
Step 12 – Wiggle Test the Harness
Monitor live data while gently moving:
- Engine harness
- Throttle connector
- Pedal connector
- Firewall harness
- PCM connector
- Ground wires
Watch for:
- Voltage spikes
- Signal loss
- Reduced Engine Power
- Code resets
A successful wiggle test often identifies intermittent wiring faults within minutes.
Step 13 – Measure Sensor Voltage
Back-probe Sensor A.
Typical analog values:
Closed throttle:
Approximately 0.5 volts
Wide-open throttle:
Approximately 4.5 volts
An intermittent fault may briefly:
- Drop to zero
- Jump to five volts
- Freeze
- Fluctuate rapidly
Capturing these events often requires multiple attempts.
Step 14 – Verify the Five-Volt Reference
Measure the reference circuit.
Possible readings:
Normal
Approximately five volts.
Continue diagnosis.
Missing
Possible causes:
- Open wire
- Shared short
- PCM regulator problem
Unstable
Possible causes:
- Harness damage
- Connector corrosion
- Shared electrical fault
Intermittent five-volt reference failures frequently affect multiple sensors.
Step 15 – Test Sensor Ground
Inspect the sensor ground using voltage-drop testing.
Check:
- Sensor ground
- Engine ground
- PCM ground
High resistance may produce intermittent operation even when continuity appears normal.
Never rely solely on an audible continuity test.
Step 16 – Test the Signal Wire
Disconnect the sensor when appropriate.
Inspect for:
- Short to voltage
- Short to ground
- Open circuit
- Excessive resistance
Move the harness while monitoring continuity.
Broken conductors frequently pass stationary tests but fail during movement.
Step 17 – Perform Terminal Tension Testing
Inspect every connector terminal.
Replace terminals that:
- Fit loosely
- Have poor spring tension
- Show corrosion
- Have been overheated
Weak terminals are one of the most overlooked causes of intermittent electronic throttle faults.
Step 18 – Use an Oscilloscope
An oscilloscope is the preferred tool for intermittent sensor diagnosis.
A healthy waveform should remain:
- Smooth
- Continuous
- Stable
- Free of spikes
Faulty waveforms may show:
- Missing signal
- Voltage spikes
- Dropouts
- Electrical noise
- Flat sections
Repeat testing while:
- Moving the harness
- Heating the sensor
- Cooling the sensor
- Applying gentle connector pressure
Oscilloscopes often reveal faults that multimeters completely miss.
Step 19 – Road Test With Live Data
If the fault only occurs while driving, record live data during a controlled road test.
Monitor:
- TPS A
- TPS B
- APP A
- APP B
- Engine RPM
- Vehicle speed
- Commanded throttle
- Actual throttle
Compare live data to the freeze-frame conditions.
Attempt to duplicate:
- Engine load
- Speed
- Temperature
- Acceleration
The goal is to reproduce the intermittent failure safely.
Step 20 – Review Freeze-Frame Information
Compare your testing results to the original freeze-frame.
Ask:
- Did the failure occur while accelerating?
- Was the engine cold?
- Was the vehicle idling?
- Did battery voltage drop?
- Did the failure occur over bumps?
- Was cruise control active?
Freeze-frame data often points directly toward the operating conditions needed to reproduce an intermittent fault.
Next Section
Part 2B continues with:
- Accelerator pedal diagnostics
- Electronic throttle-body testing
- Bidirectional scan-tool tests
- Wiring repairs
- TPS replacement
- Electronic throttle-body replacement
- Connector repairs
- Throttle relearn procedures
- Repair costs
- Manufacturer-specific diagnostics
- Common diagnostic mistakes
- Frequently asked questions
- Final repair verification
Together, Parts 2A and 2B create a complete professional diagnostic and repair guide for the P0124 trouble code.
Step 21 – Test the Accelerator Pedal Position Sensor
If the manufacturer identifies the Accelerator Pedal Position (APP) Sensor as Sensor “A”, evaluate both pedal sensors using live scan data.
Monitor:
- APP Sensor A
- APP Sensor B
- Accelerator pedal percentage
- Commanded throttle angle
- Actual throttle angle
Slowly depress the pedal through its full travel several times.
A healthy sensor should produce:
- Smooth voltage changes
- No sudden spikes
- No signal dropouts
- Consistent correlation with Sensor B
If APP Sensor A intermittently drops out while Sensor B remains stable, inspect:
- Pedal connector
- Pedal wiring
- Internal pedal sensor
- Ground circuit
Many manufacturers require replacement of the complete pedal assembly.
Step 22 – Inspect Pedal Operation
Before replacing the pedal assembly, inspect it for mechanical problems.
Look for:
- Loose mounting bolts
- Bent pedal arm
- Carpet interference
- Floor mat obstruction
- Water intrusion
- Dirt accumulation
- Damaged return spring
A binding pedal can occasionally produce abnormal sensor readings.
Step 23 – Test the Electronic Throttle Body
If Sensor “A” is integrated into the throttle body, inspect:
- Sensor A voltage
- Sensor B voltage
- Throttle motor operation
- Commanded throttle angle
- Actual throttle angle
If the throttle motor operates normally while Sensor A intermittently loses its signal, the internal position sensor may be failing.
Step 24 – Perform Bidirectional Testing
Professional scan tools allow electronic throttle control testing.
Command various throttle positions while monitoring:
- Commanded angle
- Actual angle
- TPS A
- TPS B
- Motor current
Possible results include:
Commanded Angle Changes — Actual Angle Does Not
Possible causes:
- Mechanical binding
- Failed throttle motor
- Internal gear damage
Actual Angle Changes — Sensor A Drops Out
Possible causes:
- Internal TPS failure
- Connector problem
- Wiring fault
Both Sensors Fail Simultaneously
Possible causes:
- Shared reference
- Shared ground
- PCM connector
- PCM fault
Step 25 – Compare Throttle Data to MAP and MAF
Throttle position should closely match changes in:
- MAP sensor
- MAF sensor
- Engine load
- Engine RPM
If airflow changes normally while Sensor A intermittently drops out, the airflow system is likely functioning correctly.
Focus diagnosis on the electrical circuit.
Step 26 – Inspect Aftermarket Accessories
Many intermittent throttle faults begin after installation of:
- Pedal boosters
- Throttle controllers
- Performance tuners
- Remote-start systems
- Alarm systems
Inspect every aftermarket connection carefully.
Loose adapters frequently trigger intermittent throttle codes.
Step 27 – Review Recent Repairs
Ask whether the vehicle recently received:
- Throttle-body replacement
- Battery replacement
- Engine replacement
- Intake manifold repairs
- Dashboard work
- Wiring repairs
- PCM programming
Many intermittent wiring faults begin immediately after unrelated repairs.
Step 28 – Check Technical Service Bulletins
Before replacing expensive components, search manufacturer Technical Service Bulletins (TSBs).
Look for bulletins involving:
- Connector repairs
- Harness routing
- Electronic throttle updates
- Accelerator pedal failures
- Software updates
- Reduced Engine Power complaints
Factory bulletins often identify known failure points.
Step 29 – Verify PCM Power and Grounds
Inspect:
- PCM battery power
- Ignition power
- PCM grounds
- Connector terminals
- Water intrusion
- Corrosion
Poor PCM grounds can create intermittent sensor failures throughout the vehicle.
Step 30 – Test the Circuit at the PCM
If the sensor appears normal, back-probe the PCM connector.
Possible findings:
Normal Voltage at Sensor and PCM
Possible causes:
- Software issue
- Intermittent internal PCM failure
Correct at Sensor — Incorrect at PCM
Possible causes:
- Wiring resistance
- Broken conductor
- Loose connector
- Damaged splice
Incorrect at Both Locations
Possible causes:
- Failed sensor
- Shared wiring fault
- Reference voltage problem
- Ground issue
Step 31 – Consider PCM Software
Some manufacturers have released calibration updates addressing intermittent throttle-position faults.
Programming should always be performed with:
- Stable battery voltage
- Approved programming equipment
- Current factory calibration
Software updates cannot repair damaged wiring.
Step 32 – Consider PCM Failure
PCM failure is uncommon.
Only consider PCM replacement after verifying:
- Sensor operation
- Wiring integrity
- Five-volt reference
- Ground circuits
- Connector condition
- Software updates
- Related sensor operation
Replacing the PCM should always be the final step—not the first guess.
How to Fix P0124
The correct repair depends on the diagnostic results.
Common repairs include:
- Replacing a faulty throttle-position sensor
- Replacing an accelerator pedal assembly
- Repairing damaged wiring
- Repairing intermittent grounds
- Replacing damaged connectors
- Replacing an electronic throttle body
- Removing aftermarket pedal controllers
- Updating PCM software
- Replacing the PCM (rare)
Replacing the Throttle Position Sensor
If the TPS is serviceable separately:
- Disconnect the battery if required.
- Disconnect the connector.
- Remove the mounting screws.
- Install the replacement sensor.
- Adjust if applicable.
- Tighten fasteners.
- Reconnect the wiring.
- Perform throttle relearn.
- Verify live data.
Many modern throttle bodies do not allow separate TPS replacement.
Replacing the Electronic Throttle Body
General procedure:
- Disconnect the battery.
- Remove the intake duct.
- Disconnect electrical connectors.
- Remove coolant hoses if equipped.
- Remove mounting bolts.
- Install a new gasket.
- Install the replacement throttle body.
- Torque fasteners to specification.
- Reconnect wiring.
- Perform throttle adaptation.
- Clear codes.
- Verify operation.
Replacing the Accelerator Pedal Assembly
Typical replacement steps include:
- Disconnect battery power.
- Disconnect the pedal connector.
- Remove mounting hardware.
- Install the replacement assembly.
- Tighten fasteners.
- Reconnect wiring.
- Perform calibration if required.
- Verify APP Sensor A and B operation.
Wiring Repairs
Repair damaged wiring by:
- Removing damaged sections completely
- Using the correct wire gauge
- Installing sealed automotive splices
- Applying adhesive-lined heat shrink
- Protecting repairs with loom
- Routing wiring away from exhaust heat and moving parts
Avoid temporary repairs using household connectors or electrical tape alone.
Connector Repairs
Replace connectors that exhibit:
- Broken locking tabs
- Loose terminals
- Corrosion
- Heat damage
- Missing seals
- Moisture contamination
OEM-quality connector pigtails are recommended whenever available.
Throttle Relearn Procedures
Many vehicles require throttle adaptation after:
- TPS replacement
- Throttle-body replacement
- Throttle-body cleaning
- Battery disconnection
- PCM programming
- Electronic throttle repairs
Relearn methods may include:
- Scan-tool initialization
- Ignition cycling
- Idle relearn
- Accelerator-pedal sequence
- Drive cycle
Always follow manufacturer procedures.
Verifying the Repair
After completing repairs:
- Clear all DTCs.
- Perform throttle relearn.
- Start the engine.
- Monitor live data.
- Compare Sensor A and Sensor B.
- Verify smooth throttle operation.
- Road test the vehicle.
- Recheck pending codes.
- Confirm Reduced Engine Power mode does not return.
- Confirm normal transmission operation and cruise control.
Because P0124 is intermittent, an extended road test is recommended before considering the repair complete.
Typical Repair Costs
| Repair | Typical Cost |
|---|---|
| Diagnostic testing | $100–250 |
| Wiring repair | $150–500 |
| Connector replacement | $150–400 |
| TPS replacement | $100–350 |
| Accelerator pedal assembly | $150–600 |
| Electronic throttle body | $300–1,200+ |
| PCM software update | $100–300 |
| PCM replacement | $1,000–3,000+ |
Actual costs vary depending on the vehicle manufacturer and local labor rates.
Common Diagnostic Mistakes
Avoid these common mistakes:
- Replacing the throttle body without confirming the fault
- Ignoring intermittent wiring problems
- Skipping wiggle testing
- Ignoring freeze-frame data
- Testing continuity without load
- Overlooking terminal tension
- Forgetting aftermarket pedal controllers
- Ignoring TSBs
- Skipping throttle relearn procedures
- Replacing the PCM too early
Intermittent electrical faults reward patience—not parts cannon diagnostics.
Manufacturer-Specific Notes
General Motors
Inspect:
- APP correlation
- TPS correlation
- Reduced Engine Power history
- Connector terminal tension
Ford
Monitor:
- TP Sensor 1
- TP Sensor 2
- APP Sensors
- Desired vs. actual throttle angle
Harness movement near the throttle body is a known concern on some models.
Toyota and Lexus
Verify:
- TPS correlation
- APP correlation
- Throttle initialization
- Idle relearn
Connector corrosion should be ruled out before replacing the throttle body.
Honda and Acura
Inspect:
- Accelerator pedal connector
- Throttle-body connector
- Ground integrity
- Wiring near the intake manifold
OEM replacement components are recommended.
Nissan and Infiniti
After repairs, perform:
- Accelerator Pedal Released Position Learning
- Throttle Valve Closed Position Learning
- Idle Air Volume Learning
Skipping these procedures may result in recurring drivability issues.
Hyundai and Kia
Inspect:
- Harness routing
- Connector seals
- Moisture intrusion
- Electronic throttle-body operation
Volkswagen and Audi
Throttle adaptation is commonly required after:
- Battery disconnection
- Throttle-body replacement
- Cleaning
- Software updates
BMW and MINI
Use manufacturer-level diagnostics to evaluate:
- Pedal values
- Throttle adaptation
- Signal plausibility
- Intermittent electronic faults
Chrysler, Dodge, Jeep, and Ram
Inspect:
- ETC connectors
- Accelerator pedal assembly
- Shared ground circuits
- Electronic throttle-body wiring
Frequently Asked Questions
What usually fixes P0124?
The most common repairs include replacing a failing throttle-position sensor, repairing damaged wiring, replacing loose connectors, replacing an accelerator pedal assembly, or repairing intermittent ground circuits.
Can I drive with P0124?
Driving is not recommended because intermittent throttle faults can suddenly trigger Reduced Engine Power mode or poor throttle response.
Does P0124 always mean the throttle body is bad?
No. Wiring, connectors, pedal sensors, and ground faults are more common than complete throttle-body failure.
Can a loose connector cause P0124?
Yes. Loose connector terminals are one of the most common causes of intermittent throttle-position faults.
Can heat cause P0124?
Yes. Heat can expand damaged wiring, increase resistance, or expose failing electronic components.
Why does P0124 only happen over bumps?
Vehicle vibration often causes damaged wires or loose terminals to momentarily lose contact.
Final Thoughts
The P0124 Throttle/Pedal Position Sensor “A” Circuit Intermittent code indicates that the PCM has detected an unstable or unreliable signal from the primary throttle or accelerator-pedal position sensor.
Unlike permanent high- or low-voltage faults, intermittent failures often occur only under specific driving conditions, making careful diagnosis essential.
Successful repairs depend on confirming:
- Stable live-data signals
- Proper five-volt reference
- Reliable sensor ground
- Healthy wiring
- Secure connector terminals
- Correct throttle-body operation
- Proper accelerator-pedal operation
Avoid replacing expensive components until the intermittent fault has been positively identified.
A methodical diagnosis saves time, money, and frustration—and prevents the Check Engine Light from becoming your most persistent passenger.
Continue Your Pro Street DTC Series
Related guides include:
- P0120 – Throttle/Pedal Position Sensor “A” Circuit Malfunction
- P0121 – Throttle/Pedal Position Sensor “A” Range/Performance
- P0122 – Throttle/Pedal Position Sensor “A” Circuit Low Input
- P0123 – Throttle/Pedal Position Sensor “A” Circuit High Input
- P0220–P0224 – Throttle/Pedal Position Sensor “B” Codes
- P2100–P2112 – Electronic Throttle Actuator Codes
- P2120–P2138 – Accelerator Pedal Position Sensor Codes
These articles provide additional troubleshooting information for related electronic throttle-control and accelerator-pedal system faults.
