P0375 Code: Timing Reference High-Resolution Signal “B” Malfunction

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.