The P0376 code means the powertrain control module counted more high-resolution timing-reference Signal “B” pulses than expected during a measured engine cycle.
Extra pulses can make the PCM calculate an incorrect engine or injection-pump position. Common causes include electrical interference, a damaged encoder disc, optical contamination, incorrect sensor clearance, poor signal shielding or a failing timing-reference sensor.
This code is commonly associated with electronically controlled diesel injection systems, although its exact application varies by manufacturer. The “B” identifies a particular timing-reference circuit—it does not automatically mean Bank 2, Sensor 2 or Ignition Coil “B.”
P0376 Quick Reference
| Item | Details |
|---|---|
| Code | P0376 |
| Definition | Timing Reference High-Resolution Signal “B” Too Many Pulses |
| System | Engine-position or injection-timing reference |
| Primary fault | Excessive Signal “B” pulse count |
| Common causes | Electrical noise, damaged encoder, contaminated optical path or failing sensor |
| Common symptoms | Hard starting, rough running, hesitation, stalling or reduced power |
| Severity | Moderate to serious |
| Safe to drive? | Not recommended if drivability symptoms are present |
| Best diagnostic tool | Scan tool and oscilloscope |
Browse the complete P-series OBD-II code list or visit the Pro Street OBD-II Doctor for additional diagnostic guides.
What Does the P0376 Code Mean?
P0376 is stored when the PCM receives more Signal “B” transitions than its programmed strategy expects.
The PCM knows approximately how many pulses should occur during a defined crankshaft, camshaft or injection-pump rotation. If the detected count exceeds that threshold, the controller determines that false or duplicate pulses are entering the circuit.
Depending on the application, Signal “B” may originate from:
- An optical sensor inside a diesel injection pump
- A secondary timing-reference sensor
- A crankshaft position sensor
- A distributor-mounted optical sensor
- A Hall-effect sensor
- A magnetic position sensor
- A slotted encoder disc
- A toothed reluctor wheel
- A pump-mounted electronic module
The exact component must be identified using manufacturer service information.
How Signal “B” Generates Timing Pulses
Many high-resolution timing systems use an optical sensor and encoder disc.
The encoder contains accurately positioned slots. As the disc rotates, the slots interrupt or permit light to reach the sensor. Each light transition becomes an electrical pulse.
Other systems use Hall-effect or magnetic sensors that monitor a toothed reluctor wheel. Each passing tooth creates a voltage transition or alternating-current event.
The PCM may use these pulses to calculate:
- Engine position
- Injection-pump position
- Engine speed
- Fuel-injection timing
- Injection-event synchronization
- Ignition timing
- Correlation with Signal “A”
- Combustion-event consistency
A normal waveform has a consistent number of pulses with clean edges and predictable spacing. A P0376 waveform contains additional transitions that the PCM interprets as extra position events.
What Creates Extra Timing Pulses?
False pulses generally originate from one of two categories: physical encoder problems or electrical signal corruption.
Physical causes
A cracked, warped or contaminated encoder disc can create additional optical transitions. A damaged reluctor wheel may produce irregular edges that the sensor interprets as extra teeth.
Possible physical faults include:
- Cracked encoder slot
- Warped encoder disc
- Damaged reluctor tooth
- Loose encoder or reluctor
- Excessive shaft movement
- Incorrect sensor air gap
- Metal debris attached to a magnetic sensor
- Contamination across an optical path
Electrical causes
Electrical interference can place unwanted voltage transitions onto the signal wire.
Possible sources include:
- Damaged signal shielding
- Wiring routed near ignition components
- Alternator electrical noise
- Poor sensor ground
- Loose connector terminals
- Short between signal circuits
- Failing sensor electronics
- Poorly installed aftermarket equipment
To the PCM, an electrical spike can resemble a legitimate timing pulse. Computers are extremely literal. If the spike looks like a pulse, it gets counted like one.
Common P0376 Symptoms
Symptoms depend on the severity and frequency of the extra pulses.
Common symptoms include:
- Illuminated Check Engine Light
- Extended cranking
- Hard starting
- Intermittent no-start condition
- Rough idle
- Hesitation
- Uneven acceleration
- Reduced engine power
- Poor throttle response
- Engine stalling
- Limp mode
- Increased fuel consumption
- Abnormal diesel combustion noise
- Increased exhaust smoke
- Additional timing or synchronization codes
A minor pulse-count error may only illuminate the Check Engine Light. Frequent false pulses can cause the PCM to calculate incorrect injection or ignition timing.
Common Causes of P0376
Possible causes include:
- Failing timing-reference Sensor “B”
- Contaminated optical sensor
- Dirty encoder disc
- Cracked encoder slot
- Warped encoder disc
- Damaged reluctor wheel
- Metal debris on a magnetic sensor
- Incorrect sensor air gap
- Loose sensor mounting
- Excessive shaft or bearing movement
- Damaged signal-wire shielding
- Electrical interference
- Signal wire routed near ignition wiring
- Short between sensor circuits
- Short to voltage
- Poor sensor ground
- Unstable sensor supply voltage
- Corroded connector terminals
- Loose or backed-out terminals
- Injection-pump electronics failure
- PCM connector damage
- Incorrect aftermarket wiring
- PCM software problem
- Internal PCM failure
P0376 rarely justifies immediately replacing an injection pump. Inspecting the wiring and viewing the waveform costs considerably less and involves fewer opportunities for financial regret.
How Serious Is P0376?
P0376 is a moderate-to-serious fault.
Incorrect pulse counts can cause the PCM to miscalculate engine or injection-pump position. That may result in:
- Incorrect injection timing
- Hard starting
- Rough running
- Loss of power
- Engine stalling
- Complete no-start
- Reduced-power operation
A vehicle that runs normally may be driven a short distance for diagnosis. Stop driving if it stalls, loses power, runs harshly or becomes difficult to restart.
P0376 Compared With Related Codes
| Code | Meaning | Diagnostic focus |
| P0371 | Signal “A” Too Many Pulses | Excessive pulse count on Signal “A” |
| P0374 | Signal “A” No Pulses | Complete loss of Signal “A” |
| P0375 | Signal “B” Malfunction | General Signal “B” fault |
| P0376 | Signal “B” Too Many Pulses | Excessive Signal “B” pulse count |
| P0377 | Signal “B” Too Few Pulses | Insufficient Signal “B” pulse count |
| P0378 | Signal “B” Intermittent/Erratic | Unstable or dropping Signal “B” pulses |
| P0379 | Signal “B” No Pulses | Complete loss of Signal “B” pulses |
P0376 should remain focused on extra pulses. Missing, unstable and absent pulses belong to their own code pages.
P0376 Versus P0371
P0371 and P0376 describe the same general waveform problem but on different circuits:
- P0371 applies to high-resolution Signal “A.”
- P0376 applies to high-resolution Signal “B.”
The two circuits may use different sensor channels, encoder tracks, wires or PCM terminals. Link the pages together for comparison, but do not merge their target keywords.
P0376 Versus P0375
P0375 is a general Signal “B” malfunction.
P0376 is more specific. It means Signal “B” is present, but the PCM counts more pulses than expected.
How to Diagnose the P0376 Code
1. Scan All Modules
Connect a capable scan tool and record:
- Stored codes
- Pending codes
- Freeze-frame information
- Engine speed
- Battery voltage
- Camshaft and crankshaft synchronization
- Injection timing
- Signal “A” and Signal “B” data, when available
Do not clear the codes until this information has been saved.
Freeze-frame data can reveal whether the excessive pulse count occurred during cranking, acceleration, steady cruising or a hot restart.
2. Identify Signal “B”
Use the correct wiring diagram to determine:
- Which sensor produces Signal “B”
- Whether it is optical, Hall-effect or magnetic
- Sensor power, ground and signal terminals
- PCM input terminal
- Expected pulse count
- Expected voltage range
- Correct waveform
- Specified sensor air gap
Do not assume Signal “B” means Bank 2 or Camshaft Sensor “B.” Those are separate naming systems.
3. Check for Technical Service Information
Search manufacturer information for:
- Known sensor failures
- Harness-routing problems
- Injection-pump connector faults
- Optical contamination
- Encoder-disc revisions
- PCM calibration updates
- Required relearn procedures
A published manufacturer procedure should take priority over a generic diagnostic sequence.
4. Inspect the Wiring and Connector
Inspect the complete Signal “B” circuit.
Look for:
- Loose connectors
- Bent pins
- Backed-out terminals
- Weak terminal tension
- Corrosion
- Water intrusion
- Oil or fuel contamination
- Chafed wiring
- Pinched harness sections
- Wiring routed close to ignition coils
- Wiring routed close to alternator cables
- Damaged shielding
- Poor aftermarket splices
A missing shield or poor ground may allow electromagnetic interference to add false transitions to the signal.
5. Check Battery and Charging Voltage
Test:
- Battery state of charge
- Cranking voltage
- Alternator output
- Alternator ripple
- Positive-cable voltage drop
- Ground-cable voltage drop
- Engine and PCM grounds
Excessive alternator ripple can introduce noise into sensitive sensor circuits. Low voltage may also distort sensor output or affect PCM signal processing.
6. Verify Sensor Power and Ground
Back-probe the Sensor “B” connector according to the manufacturer’s procedure.
Verify:
- Correct supply voltage
- Stable reference voltage
- Reliable ground
- Minimal ground-side voltage drop
- No voltage fluctuations
- No short between sensor circuits
A poor ground can shift the waveform voltage and create false switching events.
7. Inspect the Signal With an Oscilloscope
An oscilloscope is the most useful tool for diagnosing P0376.
A normal waveform should show:
- Clean switching edges
- Consistent amplitude
- Predictable pulse spacing
- The correct number of pulses
- Smooth frequency changes as RPM increases
A P0376 waveform may show:
- Extra narrow pulses
- Duplicate switching edges
- High-frequency noise
- Irregular transitions
- False pulses between valid pulses
- Ringing around the waveform edges
- Extra events at a particular RPM
Capture the signal during the operating conditions recorded in the freeze-frame data.
8. Compare the Sensor and PCM Waveforms
Measure Signal “B” at the sensor and again at the PCM.
Possible results include:
- Extra pulses at both locations: Inspect the sensor, encoder, reluctor and sensor power or ground.
- Clean waveform at the sensor but extra pulses at the PCM: Inspect signal-wire shielding, harness routing and interference.
- Clean waveform at both locations: Check PCM connector tension, software updates and code-setting conditions.
This comparison separates a sensor-generated problem from one introduced by the wiring.
9. Compare Signals “A” and “B”
Use a dual-channel oscilloscope when possible.
Compare:
- Pulse count
- Phase relationship
- Frequency
- Voltage amplitude
- Response to changing RPM
If Signal “A” remains clean while Signal “B” develops extra pulses, focus on the Signal “B” sensor channel and wiring.
If both signals show similar interference, inspect shared grounds, power supplies, charging-system noise or module problems.
10. Perform an Interference Test
Watch the Signal “B” waveform while operating electrical loads such as:
- Headlights
- Blower motor
- Rear defroster
- Cooling fans
- Alternator under load
Also examine the waveform as engine speed changes.
If noise increases with electrical load or alternator speed, test alternator ripple and inspect harness routing.
Temporarily moving the signal harness away from a suspected interference source may help identify improper routing. Do not permanently reroute wiring until the manufacturer’s requirements are confirmed.
11. Inspect the Encoder or Reluctor
If the electrical circuit appears correct, inspect the physical pulse-generating components.
Look for:
- Cracked encoder slots
- Additional unintended openings
- Warped encoder disc
- Contamination across slot edges
- Damaged reluctor teeth
- Metal debris
- Loose reluctor wheel
- Excessive sensor clearance
- Sensor contact with the rotating wheel
- Excessive shaft movement
A cracked optical slot may create two transitions where the PCM expects one.
12. Check Sensor Mounting and Air Gap
Verify that the sensor is:
- Fully seated
- Properly aligned
- Securely mounted
- Free from physical damage
- Positioned at the specified air gap
An incorrect air gap may create weak or distorted waveform edges that cross the PCM’s switching threshold multiple times.
13. Inspect Injection-Pump Electronics
On affected diesel applications, inspect:
- Internal optical sensor
- Encoder disc
- Pump connector
- Internal wiring
- Pump-mounted driver module
- Pump shaft and bearings
- Injection-pump drive timing
Do not replace the complete injection pump until external wiring, supply voltage, grounds and waveform integrity have been tested.
14. Evaluate the PCM Last
Consider the PCM only after verifying:
- Correct sensor power and ground
- A clean sensor output
- Proper signal-wire shielding
- Correct encoder condition
- Stable PCM power and grounds
- Proper connector terminal tension
- Applicable software updates
PCM failure is possible, but it is considerably less common than a sensor, connector, wiring or encoder problem.
Common P0376 Diagnostic Mistakes
Treating P0376 Like P0375
P0375 is a general Signal “B” malfunction. P0376 specifically identifies excessive pulses.
Replacing the Sensor Without Viewing the Waveform
Extra pulses may be introduced by wiring interference after the signal leaves the sensor.
Ignoring Signal Shielding
A circuit can pass continuity testing while still collecting electrical noise from nearby components.
Ignoring Alternator Ripple
A failing alternator diode can introduce electrical noise that affects sensor circuits.
Confusing Signal “B” With Ignition Coil “B”
P0352 concerns Ignition Coil “B.” P0376 does not identify a coil or cylinder.
Replacing the Injection Pump Too Early
Verify the waveform at the sensor and PCM before condemning a complete injection-pump assembly. Expensive guessing is still guessing.
Common P0376 Repairs
Possible repairs include:
- Cleaning and securing the sensor connector
- Replacing damaged connector terminals
- Repairing shorted or damaged wiring
- Restoring signal-wire shielding
- Correcting improper harness routing
- Repairing sensor power or ground
- Replacing Sensor “B”
- Cleaning the optical sensor or encoder disc
- Correcting the sensor air gap
- Replacing a damaged encoder disc
- Replacing a damaged reluctor wheel
- Repairing excessive shaft movement
- Repairing injection-pump electronics
- Replacing a failing alternator
- Updating PCM software
- Replacing and programming a confirmed defective PCM
- Performing a required timing or crankshaft relearn
If a variation relearn is required after repairs, see the P0315 crankshaft position variation guide.
Estimated P0376 Repair Costs
| Repair | Estimated cost |
| Diagnostic testing | $100–$250 |
| Connector or wiring repair | $100–$450 |
| Ground or shielding repair | $100–$400 |
| Alternator replacement | $400–$1,100 |
| Timing-reference sensor replacement | $180–$700 |
| Encoder or reluctor repair | $350–$1,300 |
| Injection-pump electronics repair | $500–$1,800 |
| Injection-pump replacement | $1,000–$4,000+ |
| PCM software update | $100–$300 |
| PCM replacement and programming | $700–$2,000+ |
Actual costs depend on the vehicle, component accessibility and local labor rates.
Can You Drive With P0376?
A vehicle with no symptoms may be driven a short distance for diagnosis. Continued driving is not recommended if the engine hesitates, loses power, stalls or becomes difficult to restart.
False timing pulses can cause incorrect injection or ignition calculations. The fault may also worsen until the PCM loses synchronization completely.
How to Verify the Repair
After completing the repair:
- Clear stored and pending codes.
- Confirm battery and charging voltage.
- Start the engine and monitor synchronization data.
- Observe Signal “B” with an oscilloscope.
- Compare the pulse count with manufacturer specifications.
- Compare Signal “B” with Signal “A.”
- Test under different electrical loads.
- Allow the engine to reach operating temperature.
- Reproduce the original freeze-frame conditions.
- Rescan for pending codes.
A successful repair produces the correct pulse count without duplicate edges, electrical noise or unexpected transitions.
P0376 Frequently Asked Questions
What does the P0376 code mean?
P0376 means the PCM detected too many pulses from timing-reference high-resolution Signal “B.”
What causes extra Signal “B” pulses?
Common causes include electrical interference, damaged shielding, a cracked encoder disc, contaminated optical components, incorrect sensor clearance or a failing sensor.
Can alternator problems cause P0376?
Yes. Excessive alternator ripple can introduce electrical noise into sensitive timing-reference circuits.
Is Signal “B” the same as Bank 2?
No. Signal “B” is a specific timing-reference circuit and does not universally identify Bank 2.
Can P0376 cause a no-start?
Yes. If false pulses prevent accurate synchronization, the PCM may delay or disable ignition or fuel injection.
What is the difference between P0375 and P0376?
P0375 is a general Signal “B” malfunction. P0376 specifically means the PCM counted too many Signal “B” pulses.
What is the difference between P0371 and P0376?
P0371 applies to excessive pulses on Signal “A.” P0376 applies to excessive pulses on Signal “B.”
Do you need an oscilloscope to diagnose P0376?
An oscilloscope is strongly recommended because it reveals duplicate edges, narrow false pulses and electrical noise that a multimeter cannot display.
Final Thoughts
P0376 means timing-reference Signal “B” contains more pulses than the PCM expects. The additional transitions may come from physical encoder damage or electrical interference entering the signal circuit.
Identify the correct Signal “B” source, inspect the connector and shielding, test alternator ripple and compare the waveform at the sensor and PCM. That evidence will separate a sensor or encoder problem from harness interference.
Extra pulses do not mean the engine suddenly developed extra positions. They mean the signal is lying to the PCM—and the job is figuring out who taught it to lie.
For additional diagnostic coverage, visit the Pro Street OBD-II Doctor and the complete P-series OBD-II code index.