The P0375 code means the powertrain control module has detected a malfunction involving timing-reference high-resolution Signal “B.”
This signal helps the PCM determine precise engine, crankshaft or fuel-injection-pump position. Depending on the vehicle, the problem may involve a failed position sensor, damaged wiring, unstable sensor power, contaminated optical components, an encoder or reluctor problem, or a faulty PCM input.
P0375 is commonly associated with electronically controlled diesel injection systems, but the exact component identified as Signal “B” varies by manufacturer. Consult the correct wiring diagram before replacing parts. Signal “B” is a circuit designation—not an invitation to guess which sensor the engineers buried under everything else.
P0375 Quick Reference
| Item | Details |
|---|---|
| Code | P0375 |
| Definition | Timing Reference High-Resolution Signal “B” Malfunction |
| System | Engine-position or injection-timing reference |
| Primary fault | General malfunction involving Signal “B” |
| Common causes | Failed sensor, wiring damage, poor power or ground, encoder damage or optical contamination |
| Common symptoms | Hard starting, stalling, rough running, reduced power or no-start |
| Severity | Moderate to serious |
| Safe to drive? | Not recommended if the engine stalls or loses power |
| Best diagnostic tools | Scan tool, multimeter and oscilloscope |
For additional definitions, visit the complete P-series OBD-II code list or browse the Pro Street OBD-II Doctor.
What Does the P0375 Code Mean?
P0375 is stored when the PCM determines that high-resolution timing-reference Signal “B” is missing, implausible or otherwise outside the expected operating pattern.
Depending on the application, the signal may come from:
- An optical sensor inside an electronically controlled injection pump
- A crankshaft position sensor
- A distributor-mounted optical pickup
- A Hall-effect timing sensor
- A magnetic position sensor
- A slotted encoder disc
- A toothed reluctor wheel
- A pump-mounted control module
- An ignition-control module
The PCM compares Signal “B” with other engine-position inputs. If the pulse frequency, voltage, timing or correlation does not agree with expected values, it may store P0375.
P0375 is the general malfunction code for Signal “B.” More specific codes may identify excessive pulses, insufficient pulses, intermittent operation or complete signal loss.
What Does Signal “B” Identify?
Signal “B” does not have one universal physical location.
On one vehicle, it may identify a secondary timing-reference channel inside an injection pump. On another, it may identify a separate crankshaft, distributor or control-module signal.
It also does not necessarily mean:
- Bank 2
- Sensor 2
- The second cylinder bank
- Ignition Coil “B”
- Camshaft Position Sensor “B”
The correct component must be identified using manufacturer service information.
This distinction prevents P0375 from competing with pages covering P0352 Ignition Coil “B” or camshaft Sensor “B” faults. Similar letters, completely different circuits—because automotive terminology apparently needed more opportunities for confusion.
How the High-Resolution Timing Signal Works
Many high-resolution timing systems use an optical sensor and rotating encoder disc.
The disc contains precisely arranged slots. As it rotates, light passes through the slots and reaches the sensor. Each transition produces an electrical pulse. The resulting pulse train allows the PCM to calculate exact rotational position.
Other applications use Hall-effect or magnetic sensors that read a toothed reluctor wheel. These sensors create digital or alternating-current waveforms corresponding with engine movement.
The PCM may use Signal “B” to calculate or verify:
- Crankshaft position
- Injection-pump position
- Engine speed
- Fuel-injection timing
- Injection-event synchronization
- Ignition timing
- Correlation with Signal “A”
- Combustion-event consistency
A healthy waveform has predictable amplitude, frequency and pulse spacing. A malformed waveform may cause the PCM to lose timing accuracy or synchronization.
Common P0375 Symptoms
Symptoms depend on how badly the signal has failed and whether the PCM can substitute another position input.
Common symptoms include:
- Illuminated Check Engine Light
- Extended cranking
- Intermittent no-start
- Crank-no-start condition
- Engine stalling
- Rough idle
- Hesitation
- Reduced engine power
- Poor throttle response
- Limp mode
- Uneven engine operation
- Increased fuel consumption
- Increased diesel exhaust smoke
- Hard starting when hot
- Additional timing or position-sensor codes
A minor waveform problem may only illuminate the Check Engine Light. A complete loss of synchronization can prevent the engine from starting.
Common Causes of P0375
Possible causes include:
- Failed timing-reference sensor
- Failed optical sensor
- Damaged Hall-effect or magnetic sensor
- Loose sensor connector
- Bent or backed-out connector terminals
- Corrosion inside the connector
- Water, oil or fuel contamination
- Open signal circuit
- Short to ground
- Short to voltage
- High resistance in the signal wire
- Missing sensor supply voltage
- Failed sensor ground
- Damaged signal shielding
- Electrical interference
- Incorrect sensor air gap
- Contaminated optical path
- Cracked or warped encoder disc
- Damaged reluctor wheel
- Loose reluctor or encoder
- Excessive shaft movement
- Injection-pump drive problems
- Failed pump-mounted electronics
- Low cranking voltage
- PCM connector damage
- PCM software problem
- Internal PCM failure
P0375 does not automatically mean the injection pump has failed. External wiring and connector problems should be eliminated before condemning one of the most expensive components in the system.
How Serious Is the P0375 Code?
P0375 should be treated as a moderate-to-serious problem.
An inaccurate timing-reference signal may cause:
- Incorrect fuel-injection timing
- Unstable engine operation
- Hard starting
- Sudden stalling
- Reduced power
- Complete no-start
A vehicle that runs normally with only an illuminated Check Engine Light may be driven a short distance for diagnosis. Stop driving if it stalls, hesitates heavily, loses power, produces abnormal combustion noise or becomes difficult to restart.
P0375 Compared With Related Codes
| Code | Meaning | Diagnostic focus |
| P0370 | Signal “A” Malfunction | General fault involving Signal “A” |
| P0371 | Signal “A” Too Many Pulses | Excessive Signal “A” pulse count |
| P0373 | Signal “A” Intermittent/Erratic | Unstable or dropping Signal “A” pulses |
| P0374 | Signal “A” No Pulses | Complete loss of Signal “A” pulses |
| P0375 | Signal “B” Malfunction | General Signal “B” circuit or waveform 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 Signal “B” pulses |
| P0379 | Signal “B” No Pulses | Complete loss of Signal “B” pulses |
P0375 establishes the general diagnostic page for Signal “B.” The later codes should remain focused on their specific waveform conditions.
P0375 Versus P0370
P0370 and P0375 are both general high-resolution timing-reference malfunction codes.
The difference is the circuit:
- P0370 applies to Signal “A.”
- P0375 applies to Signal “B.”
Do not combine both definitions into one article. Each signal may use different wiring, connectors, sensor channels or PCM terminals.
P0375 Versus P0352
P0352 identifies a fault in the primary or secondary circuit for Ignition Coil “B.”
P0375 concerns timing-reference Signal “B.” It does not identify a particular ignition coil or cylinder.
P0375 Versus P0335
P0335 identifies a crankshaft position Sensor “A” circuit malfunction.
P0375 may involve a crankshaft-derived signal on some vehicles, but it can also originate from an optical sensor, injection pump, distributor or separate timing-reference device.
How to Diagnose the P0375 Code
1. Scan All Modules
Connect a capable scan tool and record:
- Stored codes
- Pending codes
- Freeze-frame data
- Engine speed during cranking
- Battery voltage
- Camshaft and crankshaft synchronization
- Injection timing data
- Signal “A” and Signal “B” parameters, when available
Do not clear the codes until the information has been recorded.
Codes involving both timing signals may indicate a shared power supply, ground, mechanical drive or PCM problem.
2. Check for Manufacturer Information
Search the correct service information for:
- Technical service bulletins
- Updated wiring diagrams
- Known harness failures
- Injection-pump connector problems
- Sensor revisions
- PCM calibration updates
- Required relearn procedures
P0375 is a generic code, but the diagnostic process is application-specific.
3. Identify the Signal “B” Source
Determine exactly which component creates Signal “B.”
Verify:
- Sensor location
- Sensor type
- Power terminal
- Ground terminal
- Signal terminal
- PCM terminal
- Expected voltage
- Expected waveform
- Sensor air-gap specification
- Whether Signal “B” passes through another module
This is the most important early step. Testing the wrong “B” component tends to produce remarkably unhelpful results.
4. Inspect the Wiring and Connector
Inspect the Signal “B” circuit from the sensor to the PCM or associated control module.
Look for:
- Loose connectors
- Broken connector locks
- Bent pins
- Recessed terminals
- Weak terminal tension
- Corrosion
- Moisture
- Oil or fuel contamination
- Chafed insulation
- Wiring near exhaust components
- Pinched harness sections
- Poor previous repairs
- Damaged shielding
Gently tug individual wires near each connector. A conductor may be broken internally while its insulation still looks perfect.
5. Test the Battery and Charging System
Check:
- Battery state of charge
- Battery load capacity
- Cranking voltage
- Alternator output
- Positive-cable voltage drop
- Ground-cable voltage drop
- Engine-to-chassis ground
- PCM power and ground
Low cranking voltage can disrupt sensor output or prevent the PCM from processing the timing signal correctly.
6. Verify Sensor Power and Ground
Back-probe the Signal “B” sensor according to the wiring diagram.
Confirm:
- Correct supply voltage
- Stable reference voltage
- Reliable ground
- Minimal voltage drop
- No intermittent power loss
- No unwanted voltage on the ground circuit
If power or ground is missing, diagnose that circuit before replacing the sensor.
7. Check the Signal Circuit
With the correct modules disconnected and the circuit powered down, test the Signal “B” wire for:
- Continuity
- Short to ground
- Short to voltage
- Short to another circuit
- Excessive resistance
- Poor terminal contact
A continuity test alone may not expose a partially broken wire. Use loaded-circuit or voltage-drop testing when the service procedure allows it.
8. Test the Waveform
Use an oscilloscope to inspect Signal “B” during cranking, idle and controlled RPM changes.
A healthy digital waveform should have:
- Stable voltage amplitude
- Clean rising and falling edges
- Predictable frequency
- Consistent pulse spacing
- Smooth frequency increase with engine speed
A malfunctioning waveform may show:
- Weak amplitude
- Rounded or distorted edges
- Electrical noise
- Incorrect frequency
- Missing pulse groups
- Unstable pulse spacing
- A flat signal
- A signal stuck high or low
P0375 is a general malfunction code, so the waveform defect may not fit one narrower pulse-count category.
9. Compare Signals “A” and “B”
If both signals are available, capture them simultaneously with a dual-channel oscilloscope.
Compare:
- Frequency
- Timing relationship
- Phase alignment
- Signal amplitude
- Response to changing RPM
- Behavior during the fault
If Signal “A” remains stable while Signal “B” becomes distorted, focus on the Signal “B” sensor, circuit and encoder channel.
If both signals fail together, inspect their shared power supply, ground, mechanical drive or control module.
10. Inspect the Encoder or Reluctor
If the electrical circuit passes testing, inspect the component generating the waveform.
Possible faults include:
- Contaminated optical window
- Dirty encoder disc
- Cracked encoder slots
- Warped encoder disc
- Missing reluctor teeth
- Loose reluctor wheel
- Excessive sensor air gap
- Incorrect sensor installation
- Excessive shaft play
- Broken mechanical drive
Optical contamination can distort individual pulse transitions. A loose reluctor or encoder can shift the waveform relative to other timing signals.
11. Inspect Injection-Pump Operation
On applications where Signal “B” originates inside the injection pump, check:
- Internal sensor operation
- Pump-mounted wiring
- Pump connector condition
- Encoder rotation
- Pump-shaft movement
- Internal electronics
- Injection-pump drive timing
Before replacing the complete pump, confirm whether the sensor, connector or control module can be serviced separately.
12. Check Mechanical Timing
If Signal “B” is present but does not correlate with other position inputs, inspect:
- Timing belt
- Timing chain
- Timing gears
- Injection-pump timing
- Distributor timing
- Reluctor position
- Crankshaft or camshaft end play
A mechanically shifted signal can be electrically clean but still incorrect.
13. Evaluate the PCM Last
Consider PCM failure only after verifying:
- Sensor power and ground
- Signal output at the sensor
- Signal arrival at the PCM
- PCM power and ground
- Connector terminal tension
- Encoder or reluctor condition
- Mechanical timing
- Applicable software updates
Replacing the PCM before these checks is less diagnosis and more expensive optimism.
Common P0375 Diagnostic Mistakes
Assuming Signal “B” Means Bank 2
The “B” identifies a particular signal circuit. It does not universally identify a cylinder bank.
Replacing the Sensor Without Testing the Circuit
A sensor cannot produce a valid output without stable power, ground and signal wiring.
Using Only a Multimeter
A multimeter may display an acceptable average voltage while missing waveform distortion, noise or incorrect pulse spacing.
Ignoring Signal “A”
Signal “A” provides a useful comparison. If Signal “A” remains normal, shared mechanical or power-supply failures become less likely.
Replacing the Injection Pump Too Early
External connector and harness failures can imitate internal pump faults. Complete circuit testing before ordering the expensive part.
Targeting the Narrower Pulse Conditions
P0375 is the general Signal “B” malfunction page. Excessive, insufficient, intermittent and absent pulses belong to P0376 through P0379.
Common P0375 Repairs
Possible repairs include:
- Cleaning and securing the connector
- Replacing damaged connector terminals
- Repairing open or shorted wiring
- Restoring damaged shielding
- Repairing sensor power or ground
- Replacing the Signal “B” sensor
- Correcting the sensor air gap
- Cleaning the optical sensor or encoder
- Replacing a damaged encoder disc
- Replacing a damaged reluctor wheel
- Correcting mechanical timing
- Repairing injection-pump wiring
- Repairing or replacing pump electronics
- Replacing a weak battery
- Repairing battery cables or grounds
- Updating PCM software
- Replacing and programming a confirmed faulty PCM
- Performing a required timing relearn
If a crankshaft-position relearn is required after repairs, consult the P0315 crankshaft position variation guide.
Estimated P0375 Repair Costs
| Repair | Estimated cost |
| Diagnostic testing | $100–$250 |
| Connector or minor wiring repair | $100–$400 |
| Battery or ground repair | $100–$500 |
| Timing-reference sensor replacement | $180–$700 |
| Crankshaft position sensor replacement | $180–$550 |
| 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 location, required programming and local labor rate.
Can You Drive With a P0375 Code?
A short trip may be possible if the engine starts normally, runs smoothly and shows no loss of power. However, a timing-reference malfunction can deteriorate and cause stalling or a no-start condition.
Stop driving if the vehicle:
- Stalls
- Hesitates heavily
- Loses power
- Runs roughly
- Produces abnormal combustion noise
- Enters limp mode
- Becomes difficult to restart
A sudden synchronization failure can shut the engine down without much advance notice.
How to Verify the Repair
After completing the repair:
- Clear stored and pending codes.
- Confirm the battery is fully charged.
- Start the engine while monitoring synchronization data.
- Observe Signal “B” with an oscilloscope.
- Compare Signals “A” and “B,” when possible.
- Allow the engine to reach operating temperature.
- Perform a controlled road test.
- Reproduce the original freeze-frame conditions.
- Rescan for pending codes.
- Complete any required relearn procedure.
The repair is confirmed when Signal “B” remains stable and properly correlated under cranking, idle, temperature and load changes.
P0375 Frequently Asked Questions
What does the P0375 code mean?
P0375 means the PCM detected a malfunction involving timing-reference high-resolution Signal “B.”
What commonly causes P0375?
Common causes include sensor failure, damaged wiring, connector corrosion, poor sensor power or ground, optical contamination, encoder damage or injection-pump electronics failure.
Is Signal “B” the same as Bank 2?
No. Signal “B” is a circuit designation and does not universally identify Bank 2.
Can P0375 prevent an engine from starting?
Yes. If the PCM cannot determine precise engine or injection-pump position, it may delay or disable ignition or fuel delivery.
Can a weak battery cause P0375?
Yes. Low cranking voltage can affect sensor electronics and PCM signal processing.
Is P0375 an ignition-coil code?
No. P0375 concerns a high-resolution timing-reference signal. P0352 is the code associated with Ignition Coil “B.”
Is P0375 always caused by a diesel injection pump?
No. The signal source varies by manufacturer and may include an optical sensor, crankshaft sensor, distributor pickup or another timing-reference component.
How is P0375 different from P0376?
P0375 is a general Signal “B” malfunction. P0376 specifically indicates that the PCM detected too many Signal “B” pulses.
Do you need an oscilloscope to diagnose P0375?
An oscilloscope is strongly recommended because it reveals waveform amplitude, frequency, noise, pulse spacing and correlation problems that a multimeter may miss.
Final Thoughts
P0375 identifies a general malfunction involving timing-reference high-resolution Signal “B.” The correct diagnosis begins by identifying the actual Signal “B” source for the vehicle.
Check battery voltage, connectors, wiring, power and ground before replacing the sensor or injection pump. Then capture the waveform and compare it with Signal “A” or another position input.
The code tells you which signal failed. Testing determines whether the problem is electrical, electronic or mechanical—the part the parts store cannot do for you.
For more diagnostic coverage, visit the Pro Street OBD-II Doctor and the complete P-series OBD-II code index.