P0375 – Meaning, Symptoms, Causes & How to Fix It

P0375 is one of those diagnostic trouble codes that sounds scarier than it usually is, because it deals with the engine’s timing reference signal. When this code sets, your engine computer is telling you it’s not happy with the high‑resolution signal from the crankshaft or injection pump. You might notice rough running, hard starts, or just a check engine light. The good news: with a simple scan tool, some basic checks, and a little patience, you can usually track this down without throwing random parts at the car.

What Does P0375 Mean?

P0375 is defined as “Timing Reference High Resolution ‘B’ Signal Malfunction” (or similar wording depending on the manufacturer). In plain language, your ECU is seeing an incorrect or missing high‑resolution timing signal from a sensor that helps it know the exact position and speed of the crankshaft or injection pump.

Many diesel engines and some gasoline engines use a high‑resolution timing wheel and sensor to fine‑tune fuel injection and ignition timing. When that signal is erratic, out of range, or disappears, the ECU logs P0375 and may switch to a backup strategy, which can hurt performance and drivability.

Quick Reference

Code: P0375 – Timing Reference High Resolution “B” Signal Malfunction
Severity: Moderate to serious, can affect drivability
Common causes: Faulty timing sensor, damaged wiring, poor connections, timing wheel issues
Typical symptoms: Check engine light, rough running, hard starting, reduced power
Risk of damage: Possible long‑term engine or injector wear if ignored

Real-World Example / Field Notes

In the shop, I usually see P0375 on older diesels and some trucks that have seen a lot of miles or off‑road use. One common case: a customer with a diesel pickup complaining of intermittent no‑start and a flashing check engine light. The scan tool showed P0375 along with some stored misfire data. After inspection, the timing sensor harness was chafed where it rubbed on a bracket, causing an intermittent open circuit. A simple harness repair and proper routing fixed the issue, saving the customer from an unnecessary injection pump replacement.

Symptoms of P0375

Check engine light on: P0375 usually stores as a confirmed code and may illuminate the MIL.
Hard starting: The engine may crank longer than normal or require multiple attempts to start.
Rough idle: An unstable timing signal can cause an uneven or hunting idle.
Loss of power: You may feel reduced acceleration or poor performance under load.
Stalling: The engine might stall at idle or when coming to a stop, especially when hot.
Increased fuel consumption: Incorrect timing can lead to poor fuel economy.
Misfire or hesitation: You might notice hesitation on tip‑in or intermittent misfires.

Common Causes of P0375

Most Common Causes

Faulty high‑resolution timing sensor: The crankshaft position sensor, injection pump timing sensor, or cam sensor (depending on design) can fail internally or go out of spec.
Damaged wiring or connectors: Corroded pins, loose terminals, or broken wires in the sensor circuit are very common, especially near hot engine parts.
Contaminated or damaged timing wheel/reluctor: Metal debris, rust, or physical damage to the timing wheel can distort the signal.
Poor sensor mounting or air gap: An incorrect gap between sensor and tone wheel, or a loose sensor, can cause a weak or intermittent signal.
Low battery voltage or power supply issues: Weak system voltage can affect sensor output and ECU interpretation of the signal.

Less Common Causes

ECU (PCM) internal fault: Rare, but a failing engine control module can misread or misprocess a good sensor signal.
Aftermarket performance parts: Non‑OEM flywheels, crank pulleys, or injection pumps with different reluctor patterns can confuse the ECU.
Previous timing work done incorrectly: Incorrect installation of the timing wheel, pump, or chain/belt can alter the reference pattern.
Severe engine mechanical issues: Excessive crankshaft end play or damaged crankshaft can change the sensor gap and signal quality.
Water or oil intrusion: Oil leaks or coolant contamination inside the sensor connector can distort the signal.

Diagnosis: Step-by-Step Guide

You’ll want at least a basic OBD2 scan tool, a digital multimeter, and ideally access to wiring diagrams and service information for your specific vehicle. A scope (oscilloscope) is very helpful to see the sensor waveform but not absolutely required for basic checks.

Confirm the code: Scan the vehicle and verify P0375 is present. Note any other related codes (crank sensor, cam sensor, misfire, or voltage codes). Clear the codes and see if P0375 returns immediately or only after a drive.
Check live data: Look at engine RPM while cranking and running. If RPM reads zero or jumps around, that’s a strong clue the timing signal is unstable. Some scan tools show crank/cam sync status—watch that too.
Visual inspection: Locate the timing reference sensor(s) and harness. Check for rubbed‑through insulation, brittle wiring, oil‑soaked connectors, or loose plugs. Gently tug on the wires near the connectors.
Inspect the connector and pins: Unplug the sensor and look for green corrosion, bent pins, or moisture. Clean with electrical contact cleaner and reconnect securely.
Check sensor power and ground: With the key on, use a multimeter to verify the sensor has proper 5V reference (or 12V, depending on design) and a solid ground. Compare readings to service specs.
Test sensor resistance or signal: For 2‑wire magnetic sensors, measure resistance and compare to spec. For 3‑wire Hall sensors, back‑probe the signal wire and watch for a switching voltage while cranking.
Inspect the timing wheel/reluctor: If accessible, check for missing teeth, heavy rust, or metal shavings stuck to it. On some engines you may need to remove a cover or sensor to see the wheel.
Check for mechanical timing issues: If you suspect previous timing work, verify cam/crank or pump timing marks line up according to the service manual.
Advanced: scope and Mode $06: If you have access to a scope, view the crank/timing sensor waveform while cranking and idling. Also, some scan tools let you check Mode $06 data for misfire or crank signal counters that can confirm an intermittent problem.
Rule out ECU fault last: Only after confirming power, ground, wiring, sensor, and mechanical timing should you suspect the ECU. At that point, professional testing or ECU substitution may be needed.

Pro tip: Wiggle the harness and connectors while watching live data or the scope. If RPM drops out or the waveform glitches when you move the wiring, you’ve likely found an intermittent wiring fault.

Possible Fixes & Repair Costs

The exact repair depends on what you find during diagnosis, but most P0375 fixes are straightforward once you pinpoint the cause. Typical repair costs vary with vehicle make, sensor location, and labor rates in your area.

Replace timing reference sensor: $100–$350 parts and labor for most vehicles, more if access is difficult (e.g., behind timing covers).
Repair or replace wiring/connectors: $80–$250 depending on how much harness needs to be repaired and whether a pigtail connector is required.
Clean or replace timing wheel/reluctor: $150–$600 if it requires partial disassembly of the front of the engine or injection pump removal.
Correct mechanical timing: $300–$1,000+ for timing belt/chain or injection pump timing work, depending on engine design.
ECU replacement and programming: $500–$1,500+ and should be considered only after all other causes are ruled out.

Costs are affected by labor rate, how buried the sensor is, whether OEM or aftermarket parts are used, and if additional maintenance (like timing belt replacement) is done at the same time.

Can I Still Drive With P0375?

In many cases, you can still drive with P0375 for a short period, but it’s not something you should ignore. If the ECU can fall back on a lower‑resolution signal, the engine might run, just not as smoothly or efficiently. However, if the signal drops out completely, you may experience sudden stalling or a no‑start condition. If you notice severe loss of power, frequent stalling, or hard starting, avoid highway trips and heavy loads, and get the vehicle inspected as soon as possible.

What Happens If You Ignore P0375?

Ignoring P0375 can lead to chronic hard starting, increased fuel consumption, and rough running. Over time, poor timing control can stress injectors, glow plugs (on diesels), and internal engine components. You also risk being stranded if the sensor or wiring fails completely and the engine refuses to start. Addressing the issue early usually keeps repair costs lower.

Last updated: March 1, 2026

Key Takeaways

P0375 points to a problem with the engine’s high‑resolution timing reference “B” signal, often from a crank, cam, or injection pump sensor.
Common culprits are failing sensors, damaged wiring, poor connections, or a contaminated timing wheel.
Symptoms range from a simple check engine light to hard starting, rough idle, and stalling.
Basic tools and a careful inspection can usually narrow down the cause without guessing.
Driving short‑term may be possible, but ignoring the code can lead to bigger, more expensive issues.

Vehicles Commonly Affected by P0375

P0375 shows up most often on diesel pickups and SUVs that use high‑resolution timing systems, such as certain Chevrolet/GMC Duramax, Ford Power Stroke, and Dodge/Ram Cummins engines (especially older generations). It can also appear on some Volkswagen/Audi TDI models, Isuzu diesels, and a few gasoline engines that rely on detailed crank or pump timing signals. High‑mileage work trucks, vehicles used for towing, and off‑road rigs are more likely to develop wiring or sensor issues that trigger this code.

FAQ

Can P0375 clear itself?

Yes, in some cases P0375 can clear itself if the issue is intermittent, like a loose connector making temporary contact again. However, the underlying problem usually returns. It’s better to diagnose and fix the cause rather than rely on the light going off on its own.

Is P0375 caused by bad fuel?

Bad fuel by itself usually does not cause P0375. Contaminated fuel can create misfires or poor running, but this code is specifically about the timing reference signal. That said, if bad fuel causes severe knocking or stalling, it might make a marginal sensor or wiring problem show up more often.

Can a weak battery cause P0375?

A weak battery or low system voltage can contribute to P0375, especially during cranking when voltage drops. The ECU and sensors need stable voltage to generate and read clean signals. If your battery is old or the starter drags, check and correct that first, then see if the code returns.

How urgent is it to fix P0375?

You should address P0375 as soon as you reasonably can. It may not be an immediate “park it now” emergency if the engine still runs well, but the risk of sudden no‑start or stalling is there. Fixing it early also protects your engine and fuel system from long‑term timing‑related stress.

Can I replace the timing sensor myself?

On many vehicles, yes. If the sensor is easy to access and you’re comfortable with basic tools, you can often replace it at home. The key is to confirm the sensor is actually bad and not just a wiring or timing issue. Always disconnect the battery, follow torque specs, and double‑check the connector and routing of the harness.

P0375 – Timing Reference High Resolution Signal “B”