P0371 – Timing Reference High Resolution Signal “A” Too Many Pulses

P0371 is a diagnostic trouble code that points to a problem with how your engine computer reads crankshaft position. In plain terms, the ECU is seeing too many “pulses” from the crankshaft position sensor in a short amount of time, so it flags an error. This can lead to hard starting, rough running, and in some cases a no-start situation. If you just scanned your car and found P0371, you’re in the right place. Below, you’ll learn what it means, common causes, symptoms, and how you or your mechanic can fix it.

What Does P0371 Mean?

P0371 stands for “Timing Reference High Resolution Signal A – Too Many Pulses.” Your engine uses a crankshaft position (CKP) sensor and, in some systems, a high-resolution timing wheel or optical sensor to track the exact position and speed of the crankshaft. The ECU needs this information to control ignition timing and fuel injection precisely.

When the ECU sees more timing pulses than it expects in a given time window, it assumes the signal is corrupted, noisy, or the sensor/wiring is faulty. That’s when it sets P0371 and usually turns on the check engine light.

Quick Reference

• Code: P0371
• Definition: Timing Reference High Resolution Signal A – Too Many Pulses
• Main area: Crankshaft position / high-resolution timing circuit
• Typical symptoms: Hard start, misfire, rough idle, reduced power
• Risk level: Moderate to high (can lead to stalling or no-start)

Real-World Example / Field Notes

In the shop, I usually see P0371 on higher-mileage vehicles where the crank sensor has started to break down or the wiring has been cooked by exhaust heat. One case that stands out was a mid-2000s pickup that would randomly stall at stoplights. The owner had already replaced the fuel pump, plugs, and coils. Scanning the ECU showed P0371 and a few intermittent misfire codes. Oscilloscope testing revealed a crank sensor signal full of “extra” spikes. A new OEM crankshaft position sensor and a small harness repair completely solved the issue.

Symptoms of P0371

• Check engine light on: P0371 usually turns on the MIL and may store as a current or pending code.
• Hard starting: The engine may crank longer than normal or only start intermittently.
• Rough idle: An unstable timing signal can cause shaking or fluctuating idle speed.
• Engine misfire: You may feel hesitation, stumbling, or lack of smooth acceleration.
• Loss of power: The ECU may use backup strategies, reducing power and throttle response.
• Stalling: In severe cases, the engine may stall at idle or when coming to a stop.
• No-start condition: If the signal is bad enough, the engine may not start at all.
• Poor fuel economy: Incorrect timing can lead to higher fuel consumption.

Common Causes of P0371

Most Common Causes

• Failing crankshaft position sensor: Internal electronic failure or heat damage often causes extra or erratic pulses.
• Damaged tone ring / reluctor wheel: Bent, cracked, or missing teeth on the crankshaft timing wheel can create abnormal pulses.
• Wiring issues in CKP circuit: Chafed, corroded, or partially broken wires and loose connectors introduce noise and false signals.
• Poor sensor ground or power: High resistance in grounds or low reference voltage can distort the signal.
• Aftermarket or incorrect sensor: Cheap sensors sometimes produce out-of-spec signals the ECU interprets as too many pulses.

Less Common Causes

• ECU (PCM) internal fault: A failing engine computer can misread a good crank signal, though this is rare.
• Improper crank sensor installation: Incorrect air gap or sensor not fully seated can cause signal errors.
• Mechanical damage to crankshaft: Severe damage or excessive end play can misalign the tone ring.
• Electrical interference: High-current accessories, bad alternator diodes, or poor shielding can create noise on the signal wire.
• Previous engine or timing work errors: Incorrectly installed timing components, flywheel, or flexplate can offset or damage the tone ring.

Diagnosis: Step-by-Step Guide

You’ll want a good scan tool (ideally with live data and Mode $06), a digital multimeter, and if possible an oscilloscope for viewing the crank signal. A basic code reader can confirm P0371, but deeper tools make diagnosis faster and more accurate.

1. Confirm the code: Scan the vehicle and verify P0371 is present. Note any related codes like misfires (P0300–P030X) or other crank/cam sensor codes.
2. Check freeze-frame data: Look at engine speed, load, and temperature when P0371 set. This can show if it happens at start-up, idle, or higher RPM.
3. Visual inspection of wiring: Locate the crankshaft position sensor and follow the harness. Look for melted insulation, rubbing on brackets, oil saturation, or loose connectors.
4. Inspect the connector: Unplug the sensor and check for bent pins, corrosion, or moisture. Clean and apply dielectric grease if recommended.
5. Check power and ground: Using a multimeter, verify proper reference voltage (often 5V) and a solid ground at the sensor connector with key on.
6. Inspect tone ring / reluctor: If accessible, inspect the crank tone ring or flexplate teeth with a light. Look for cracks, missing teeth, or heavy rust buildup.
7. Monitor live data: With a capable scan tool, watch engine RPM and crank signal data while cranking and running. Look for sudden drops, spikes, or unrealistic RPM readings.
8. Scope the signal (if available): An oscilloscope on the CKP signal wire will show if there are extra pulses, noise, or irregular patterns at various RPMs.
9. Wiggle test: While monitoring live data or scope, gently wiggle the harness and connector. If the signal glitches, you likely have a wiring or connector issue.
10. Substitute a known-good sensor: If wiring and tone ring look good but the signal is still bad, install a quality OEM or premium aftermarket crank sensor and retest.

Pro tip: Before condemning the ECU, make absolutely sure you’ve checked the sensor air gap, tone ring condition, and wiring integrity. ECU failures on this circuit are much less common than sensor or harness problems.

Possible Fixes & Repair Costs

Most P0371 fixes involve restoring a clean, accurate crankshaft position signal. Typical repairs include replacing the crankshaft position sensor, repairing or replacing damaged wiring, cleaning or replacing a damaged tone ring, or in rare cases replacing the ECU. At a repair shop, you’re usually looking at about $150–$350 for a crank sensor replacement, $100–$400 for wiring repairs depending on complexity, and $500+ if an ECU is needed and programming is required. Labor rates, vehicle design, and parts quality all affect the final cost.

• Replace crankshaft position sensor: Most common fix; always use a reputable brand or OEM part.
• Repair or replace wiring/connector: Fix chafed wires, corroded pins, or loose terminals and secure the harness away from heat and moving parts.
• Clean or replace tone ring: Remove rust, debris, or replace a cracked or bent reluctor wheel or flexplate.
• Correct sensor mounting / air gap: Reinstall sensor properly, ensuring the correct distance to the tone ring per service manual specs.
• ECU replacement and programming: Only after all other causes are ruled out; requires proper programming or coding.

Can I Still Drive With P0371?

You might be able to drive with P0371 for a short time, but it’s not a good idea to ignore it. If the crank signal gets worse, the engine can stall unexpectedly or fail to restart, which is dangerous if you’re in traffic. In some cars, the ECU may go into a fallback mode that limits power and increases fuel consumption. If the car is running, drive gently and schedule diagnosis as soon as possible, or have it towed if starting becomes unreliable.

What Happens If You Ignore P0371?

Ignoring P0371 can turn a relatively simple sensor or wiring repair into a bigger headache. Continued driving with a bad crank signal can lead to repeated stalling, potential catalyst damage from misfires, and eventually a complete no-start situation that leaves you stranded. Addressing the code early usually keeps repair costs lower and prevents collateral damage.

Last updated: March 1, 2026

Vehicles Commonly Affected by P0371

P0371 can show up on many OBD-II vehicles, but it’s more common on certain platforms. You’ll often see it on GM trucks and SUVs (Chevrolet Silverado, GMC Sierra, Tahoe, Suburban), Chrysler/Dodge/Jeep vehicles with V6 and V8 engines, and some Volkswagen and Audi models that use high-resolution crank sensors. It also appears on various BMW and Subaru engines, especially as mileage climbs and heat cycles take their toll on sensors and wiring. Regardless of brand, the diagnostic approach is very similar.