P0371 — Timing Reference High Resolution Signal A Too Many Pulses

P0371 — Timing Reference High Resolution Signal A Too Many Pulses. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: blown fuse feeding the circuit, poor ground connection, control module driver fault.

powertrain (engine/transmission)

Is it safe to drive?

Repair promptly P0371 can cause unstable engine-speed information, stalling, or a no-start condition. Avoid extended driving if the engine stalls, loses power, or the RPM indication jumps; otherwise, drive cautiously to a repair facility and avoid heavy load.

Typical symptoms

The check-engine light may illuminate and P0371 will be stored in the powertrain control module.
The engine may crank but not start when the control module considers the high-resolution timing signal implausible.
Stalling, hesitation, or intermittent loss of power can occur when the excess-pulse condition appears.
Engine speed may fluctuate or drop suddenly, and available scan data may show unstable RPM.
A rough idle, misfire, or reduced throttle response may occur while the control module limits engine operation.
The symptom may be load-sensitive, temperature-sensitive, or most apparent during cranking and low-speed operation.

Common causes

A noisy or internally faulty crank-position sensor assigned to Timing Reference High Resolution Signal A may generate false edges and excess pulses.
Debris, corrosion, or physical damage on the reluctor or timing target can create unintended magnetic events that the control module counts as additional pulses.
A loose sensor mount or excessive sensor-to-target air gap can produce an unstable signal during vibration, low engine speed, or cranking.
Corroded terminals, damaged wiring, chafing, or poor sensor or control-module grounds can introduce noise into the high-resolution timing-reference circuit.
A faulty sensor power or reference circuit, particularly on a Hall-effect sensor, can distort the signal and create false transitions.
An incorrectly positioned sensor, damaged target wheel, or incorrect sensor installation after previous repair can cause an excessive pulse count.
A control-module input-circuit failure is possible only after the sensor, target, wiring, connectors, and grounds have been verified.

How to diagnose with an OBD scanner

Document P0371 with scan data Connect an OBD2 scanner, ELM327 adapter, or AIScanAuto and read stored codes, pending codes, and any available freeze-frame information. Record RPM, load, voltage, and whether P0371 appears during cranking or running. AIScanAuto is a diagnostic tool rather than OEM software, and generic ELM327 access may be limited.
Inspect the timing-reference sensor and target Locate the sensor designated as Timing Reference High Resolution Signal A using the vehicle wiring information. Check for debris, oil contamination, corrosion, damaged reluctor teeth, a cracked target, loose fasteners, and incorrect sensor positioning. Confirm that the target is not producing unintended events.
Test the complete signal circuit Unplug the sensor and inspect connector pins for spread, corrosion, water, or pushed-back terminals. Check wiring for opens, shorts, chafing, and poor grounds. For a Hall-effect sensor, test supply, reference, and ground; for a variable-reluctance sensor, test coil-lead continuity and resistance while moving the harness.
Measure the waveform Use an automotive oscilloscope with the correct probe setup to inspect the high-resolution reference signal. The waveform should follow the specified magnetic-event pattern without narrow false spikes or unstable transitions. Erratic live RPM supports a signal defect, but an RPM reading alone cannot count individual high-resolution pulses.
Isolate the sensor or target Compare the measured waveform with the manufacturer pattern and test the sensor with a known-good unit or approved bench procedure if the circuit passes. Replace the sensor or repair the target only when testing shows that it creates excess events; replacing parts without waveform verification can leave P0371 unchanged.
Verify the repair After correcting the fault, clear P0371 with the scan tool, perform any specified crank or cam relearn, and monitor RPM during cranking and acceleration. Confirm that P0371 does not return. If the waveform and all external circuits are correct, the control-module input circuit becomes the remaining diagnostic possibility.

Approximate repair cost

Typical independent-shop cost is approximately USD 150-700 for diagnosis and a confirmed sensor, connector, wiring, or reluctor repair. A crank-position sensor replacement commonly falls around USD 180-450 including labor, while extensive harness work or target-wheel repair can raise the total. These figures are estimates and vary by region, vehicle design, and shop.

Common questions

What does P0371 specifically mean?

P0371 means the control module is receiving too many pulses from Timing Reference High Resolution Signal A. The defect is generally in the sensor, target, or signal circuit rather than an ordinary engine-timing setting.

Can the vehicle be driven with P0371?

Driving may be possible if the signal remains stable, but stalling, power loss, or a no-start condition can occur. If P0371 is accompanied by those symptoms, stop driving and have the high-resolution reference circuit tested promptly.

What usually causes P0371?

Common causes include a noisy crank-position sensor, debris or damage on the reluctor wheel, excessive sensor air gap, poor grounds, damaged wiring, or a faulty control-module input. Waveform testing is needed to distinguish these conditions.

Does P0371 mean the engine timing is set too far advanced?

No. P0371 is an implausible pulse-count fault involving Timing Reference High Resolution Signal A. It does not directly specify excessive camshaft advance or an incorrect mechanical timing value.

When your engine control module detects that the high-resolution timing reference signal is delivering more electrical pulses than it should, it logs trouble code P0371. This diagnostic fault specifically points to an abnormality in the circuit responsible for providing precise timing information to the powertrain control module. The PCM relies on this signal to calculate exact crankshaft position, fuel injection timing, and ignition advance — so when the pulse count exceeds expected parameters, the module flags the problem and illuminates the check engine light.

The affected system works by using a toothed reluctor wheel or optical sensor to generate a rapid series of electrical pulses as the crankshaft rotates. The control module counts these pulses between defined reference points to determine engine speed and position with high precision. Normally the PCM expects a specific number of pulses per engine cycle. When self-diagnostics detect an excessive pulse count — suggesting a short to power, electrical noise, or a malfunctioning sender unit — the system registers the fault. For P0371 to fully set, the condition must persist across a programmed number of drive cycles. The freeze frame saved alongside the code shows engine RPM, load, coolant temperature, and vehicle speed the moment the problem occurred, giving you a starting point for diagnosis.

P0371 is classified as a powertrain fault, meaning it relates to engine or transmission operation. Depending on which system depends on the timing reference signal, you may experience anything from a minor performance dip to a complete loss of certain functions.

Common Symptoms of P0371

Check Engine Light stays illuminated
Noticeably higher fuel consumption in some driving conditions
The vehicle may enter limp-home mode, restricting power and speed
Affected auxiliary systems operate intermittently or stop working entirely
In rare cases, rough idle or hesitation during acceleration

What Causes P0371

Damaged or corroded electrical connectors in the timing signal circuit
Poor ground connection at the sensor or control module
Open or shorted wiring somewhere in the signal circuit
Faulty sensor or actuator generating abnormal pulse signals
Blown fuse feeding power to the affected circuit
Internal fault in the control module driver circuit

How to Diagnose P0371

Hook up an OBD2 scanner and confirm P0371 is stored. Record the freeze frame data — it reveals engine conditions when the fault triggered and tells you whether the problem occurs at idle, under load, or at operating temperature.
Pull any related diagnostic trouble codes. P0371 sometimes appears alongside other fuel or timing-related codes, and those secondary codes often point to the real root cause. Check manufacturer technical service bulletins for your specific make and model — some P0xxx faults have known software updates or factory-recommended repair procedures.
Inspect the wiring harness and connectors associated with the timing reference circuit. Look for broken insulation, corrosion buildup, bent pins, or loose plugs. A connector that looks okay may still have internal corrosion causing high resistance.
With the key on and engine off, measure reference voltage and ground at the sensor connector. Compare readings to specifications. Then check signal circuit continuity between the sensor and PCM.
Perform a wiggle test while monitoring live data. Gently move the harness and connectors while watching the PCM data stream. Any signal dropouts or spikes indicate a broken wire or intermittent connection.
Clear the code and complete a full drive cycle that replicates the freeze frame conditions. If P0371 does not return, the fault was likely temporary. Persistent recurrence confirms a genuine hardware problem.

Repair Options and Costs for P0371

Address inexpensive issues before replacing major components. Here are typical repair costs at independent shops:

Wiring repair or connector replacement: $80–$250 for parts and labor
Replacement of faulty sensor or actuator: $150–$500 depending on part price and labor time
Control module diagnosis and repair: $300–$1,000 if the PCM itself requires attention

Total Cost to Fix P0371

Your actual expense depends entirely on which part is faulty. A corroded connector or blown fuse on the cheap end might run under $100 total. Replacing a failed crankshaft position sensor or camshaft position sensor falls in the middle range. The control module route is the most expensive scenario, though it is rarely the first thing to check. An accurate diagnosis before purchasing parts is the best way to avoid overspending on P0371.

Can You Drive with P0371?

The severity is short — most vehicles remain driveable when P0371 is stored, though you may notice reduced performance, higher fuel usage, or a disabled feature like variable valve timing. Treat the fault as urgent if the car stalls, fails to start, or triggers safety-related warnings such as brake or power steering alerts. Otherwise, schedule diagnosis promptly to prevent potential damage from prolonged operation with incorrect timing signals.