P0376 – Timing Reference High Resolution Signal “B” Too Many Pulses

P0376 is one of those codes that looks scary but is very specific once you understand it. It points to a problem with the high-resolution signal from your engine’s timing or crankshaft reference system, usually involving the crankshaft position sensor, optical sensor, or the wiring feeding that signal to the ECU. When this signal is out of range or not matching what the computer expects, you can get hard starting, misfires, or even a stall. In this guide, you’ll learn what P0376 means, common causes, symptoms, and realistic repair options.

What Does P0376 Mean?

P0376 is defined as “Timing Reference High Resolution Signal ‘B’ Too Many Pulses” (wording can vary slightly by manufacturer). In plain language, your engine computer is seeing more timing reference pulses than it should from the high-resolution channel “B” of the crank or cam timing system.

Many engines use a high-resolution signal wheel (often on the crankshaft or inside the injection pump on diesels) with many teeth or slots. The ECU counts these pulses to control ignition timing and fuel injection. When it detects extra pulses, it flags P0376 because it can no longer trust that signal for precise timing control.

Quick Reference

• Code: P0376
• Meaning: Timing reference high-resolution signal “B” has too many pulses
• Main systems: Crankshaft/camshaft timing, ignition, fuel injection
• Typical culprits: Crank/cam sensor, optical wheel, wiring, ECU input fault
• Severity: Moderate to serious; can cause drivability issues and stalling

Real-World Example / Field Notes

In the shop, I most often see P0376 on older GM gasoline engines and some diesel platforms that use an optical or high-tooth-count reluctor wheel. A common scenario: the vehicle comes in with a rough idle, intermittent stall at stoplights, and a check engine light. Scan data shows erratic RPM readings or timing jumping around. On inspection, the crank sensor wiring is rubbed through on a bracket, or the optical wheel inside the distributor or pump has damage or contamination. Fix the sensor or wiring, clear the code, and the engine runs smooth again.

Symptoms of P0376

• Check engine light on: P0376 usually sets a MIL and may store as a confirmed or pending code.
• Hard starting: The engine may crank longer than normal or need multiple attempts to start.
• Rough idle: Unstable timing can cause shaking, surging, or uneven idle speed.
• Misfires or hesitation: You may feel stumbling, lack of power, or hesitation on acceleration.
• Stalling: The engine can stall at idle, when coming to a stop, or even while cruising.
• Poor fuel economy: Incorrect timing can lead to wasted fuel and lower MPG.
• Other timing-related codes: You might see additional crank/cam correlation or misfire codes stored.

Common Causes of P0376

Most Common Causes

• Faulty crankshaft position sensor: An internal failure or intermittent signal from the crank sensor is one of the top reasons this code appears.
• Damaged or dirty high-resolution wheel: A cracked, bent, missing-tooth, or contaminated reluctor/optical wheel can generate extra or distorted pulses.
• Wiring harness issues: Chafed, corroded, or oil-soaked wiring and poor connectors at the sensor or ECU can create noise or false pulses.
• Poor sensor mounting or gap: On magnetic sensors, an incorrect air gap or loose mounting can cause unstable readings at certain RPMs.
• Aftermarket parts or modifications: Non-OEM sensors, incorrect distributors, or altered timing components can change the pulse pattern.

Less Common Causes

• ECU input circuit fault: A failing engine control unit can misread a normal signal as too many pulses.
• Internal engine timing issues: Excessive crankshaft end play, worn timing components, or a slipped timing gear can distort the signal pattern.
• Electrical noise/interference: Poor grounds, high-resistance connections, or nearby high-current wiring can introduce false pulses.
• Incorrect sensor type or tooth count: Using the wrong sensor or reluctor wheel for the application can cause the ECU to see more pulses than expected.
• Previous repair errors: Misaligned distributor, wrong timing reference marks, or improperly installed pump/distributor can trigger P0376.

Diagnosis: Step-by-Step Guide

Before you start, you’ll want a basic scan tool (preferably with live data), a digital multimeter, and if possible an oscilloscope for viewing sensor waveforms. A service manual or wiring diagram for your specific vehicle is extremely helpful, especially for identifying the correct sensor wires and expected signals.

1. Confirm the code and check for companions. Use a scan tool to read all stored and pending codes. Note any crank/cam correlation or misfire codes that appear with P0376.
2. Review freeze frame data. Look at engine speed, load, and temperature when the code set. This helps you reproduce the conditions (for example, hot idle or highway cruise).
3. Perform a visual inspection. Inspect the crankshaft and camshaft sensors, connectors, and wiring. Look for rubbing, oil saturation, broken clips, corrosion, or loose plugs.
4. Check sensor power and ground. With a multimeter, verify that the sensor has proper reference voltage (often 5V), a good ground, and correct signal wire continuity back to the ECU.
5. Monitor live RPM and timing data. Watch engine RPM, crank signal status, and timing advance on the scan tool. Erratic RPM or sudden drops to zero while the engine is running point to a signal issue.
6. Scope the sensor signal (if available). Using an oscilloscope, observe the high-resolution signal waveform. Look for extra spikes, double pulses, or irregular tooth patterns that match the P0376 description.
7. Inspect the reluctor or optical wheel. If accessible, remove the sensor or cover and inspect the wheel for cracks, missing teeth, bent sections, or debris (metal shavings, oil sludge, dirt).
8. Wiggle test the harness. While monitoring live data or the scope, gently move the harness and connectors. If the signal glitches or the engine stumbles, you’ve likely found a wiring problem.
9. Check ECU grounds and power feeds. Poor ECU grounding can distort input signals. Clean and tighten engine and chassis grounds and verify voltage drops are within spec.
10. Compare with service information. Some manufacturers provide Mode $06 or specific test values for crank/cam signals. Use these to confirm whether the sensor is out of spec before replacing parts.

Pro tip: Don’t replace the ECU until you’ve verified the sensor, wiring, power, and grounds. ECU failures are far less common than bad sensors or harness issues, and misdiagnosis can get expensive fast.

Possible Fixes & Repair Costs

Repairs for P0376 range from simple wiring fixes to sensor or component replacement. Typical sensor replacement at an independent shop runs about $150–$350 including parts and labor, depending on access. Wiring repairs can range from $100 for a simple connector fix to $400+ if a section of harness must be replaced. Replacing an optical wheel or distributor assembly may cost $300–$700. ECU replacement or reprogramming is usually the most expensive, often $600–$1,200 or more. Labor rates, vehicle make, and parts availability all affect the final bill.

• Repair or replace damaged wiring/connectors at crank or cam sensors.
• Replace faulty crankshaft or camshaft position sensor with quality OEM or equivalent part.
• Clean or replace contaminated or damaged reluctor/optical wheel.
• Correct sensor mounting, spacing, or alignment issues.
• Update or reflash ECU software if a known calibration issue exists.
• Replace ECU only after all other causes are ruled out and tests confirm an internal fault.

Can I Still Drive With P0376?

In many cases you can still drive with P0376 for a short period, but it’s not wise to ignore it. If the timing reference signal degrades further, the engine may stall unexpectedly or fail to restart, leaving you stranded. You might also experience poor performance and higher fuel consumption. If the vehicle is running rough, stalling, or the check engine light is flashing, you should avoid driving and have it towed to a shop. At minimum, reduce driving and get it diagnosed soon.

What Happens If You Ignore P0376?

Ignoring P0376 can lead to repeated stalling, hard starting, and potential damage to other components from misfires or backfires. Over time, unburned fuel can overheat the catalytic converter, and intermittent stalling can create safety risks in traffic. What starts as a minor sensor or wiring issue can turn into a more expensive repair if left unchecked.

Last updated: March 1, 2026

Vehicles Commonly Affected by P0376

P0376 shows up most frequently on vehicles that use detailed high-resolution timing systems. You’ll often see it on GM products (Chevrolet, GMC, Pontiac, Buick, Cadillac) with distributor or optical crank systems, as well as some older Ford and Chrysler engines. Certain diesel trucks and vans that rely on optical or high-tooth-count wheels in the injection pump or crankshaft can also trigger this code. While any OBD-II vehicle can potentially set P0376, it’s more common on late-1990s to early-2000s platforms with complex timing reference setups.