P0371
Timing Reference High Resolution Signal A Too Many PulsesP0371 is a generic OBD-II powertrain diagnostic trouble code: Timing Reference High Resolution Signal A Too Many Pulses. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0371 means
P0371 — "Timing Reference High Resolution Signal \"A\" Too Many Pulses" — is set when the PCM counts more high-resolution pulses per crankshaft revolution (or per unit of measured angle) than the engine's reluctor ring or encoder disc should physically produce. The PCM knows exactly how many teeth, windows, or magnetic transitions the installed sensor wheel should generate per revolution; if the pulse count exceeds that expected number by more than the calibrated tolerance, the PCM concludes the signal is corrupted and stores P0371.
The most common cause is electrical noise contamination. When harness wiring for two sensors runs in close proximity without adequate shielding, crosstalk can superimpose extra pulses onto the high-resolution signal line — a second sensor's waveform effectively gets added to the first, doubling (or distorting) the pulse count. Chafed wiring that intermittently touches a rapidly switching circuit nearby produces the same effect. On optical systems, reflections or stray light from a cracked disc can create ghost pulses. A reluctor ring with an added burr or metal fragment lodged between teeth can also produce an extra transition per revolution.
Because the PCM uses the high-resolution pulse stream for precise ignition timing calculations, an over-count causes sudden, unpredictable timing shifts. The engine may experience abrupt timing retard or advance events that manifest as a sharp knock, hesitation, or power stumble during acceleration. Unlike P0370 where the signal is absent, with P0371 the signal is present but inaccurate — making the engine more likely to keep running, but with degraded or unpredictable timing behaviour.
Common causes
Most-frequently reported root causes when P0371 is logged.
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1
Electromagnetic crosstalk from adjacent sensor wiring (e.g., ignition coil primary wires, injector wires) running parallel to the high-resolution signal wire without adequate shielding.
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2
Harness chafing that allows the high-resolution signal wire to intermittently contact another rapidly switching circuit, injecting spurious pulses.
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3
Metal burr, debris fragment, or contamination lodged on the reluctor ring producing an extra magnetic transition per revolution.
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4
Cracked or damaged optical encoder disc with reflective fragments creating ghost pulses in the phototransistor.
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5
Faulty sensor with internal noise on its output stage generating extra transitions.
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6
Failed or corroded harness shield causing the signal wire to act as an antenna and pick up ignition system noise.
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7
Two sensor signals shorted together — if the signal wire for the high-resolution sensor is bridged to the standard CKP signal wire, the combined pulse count will exceed expectations.
Symptoms drivers notice
How to diagnose P0371
A typical diagnostic flow when this code is present.
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1
Connect a scan tool and record all codes; companion codes P0335 (CKP circuit), P0370 (signal malfunction), or ignition system codes may indicate the noise source.
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2
Inspect the entire high-resolution signal harness routing for areas where it runs alongside high-current switching circuits — ignition coil primaries, injector wiring, and alternator output wires are common culprits; re-route or add shielding as needed.
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3
Perform a wiggle test on the signal harness with the engine running and a live signal PID on the scan tool; induced noise dropouts or pulse bursts confirm a harness integrity problem.
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4
Inspect the harness shield (where fitted) for continuity and proper grounding at both ends; a broken shield ground dramatically increases noise susceptibility.
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5
Remove the sensor and visually inspect the reluctor ring for burrs, debris, or damaged teeth using a bore scope or by rotating the engine by hand.
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6
On optical systems, inspect the encoder disc under good lighting for cracks, reflective contamination, or foreign material between the disc windows.
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7
Substitute a known-good sensor if the wiring and reluctor ring are confirmed clean — an internally noisy sensor can generate phantom pulses that disappear when the unit is replaced.
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8
Clear codes and test drive across multiple RPM ranges while monitoring the high-resolution signal PID for anomalous pulse clustering.
Related powertrain codes
Frequently asked questions
Can P0371 cause engine knock or detonation?
Yes. If the spurious pulses cause the PCM to miscalculate crankshaft position and advance ignition timing beyond the knock threshold, actual detonation can occur. This is particularly concerning on high-compression or boosted engines. Addressing P0371 promptly reduces the risk of knock-related damage.
How is P0371 different from P0372?
P0371 is \"too many pulses\" and P0372 is \"too few pulses.\" Too many pulses typically indicates noise injection — extra signals being added to the line. Too few pulses indicates missing transitions — a damaged reluctor tooth, weak sensor, or intermittent open circuit removing expected pulses. Both corrupt the timing calculation, but they point toward different root causes and different areas of the harness and hardware to inspect.
Will repositioning the wiring harness fix P0371?
In many noise-contamination cases, yes. Separating the signal wire from high-current switching wires and securing it away from ignition and injector harnesses can eliminate the crosstalk entirely. Adding a ferrite bead or replacing a degraded shield can also resolve the code without replacing any sensors or mechanical components.
Can a software update fix P0371?
On some vehicles, PCM calibration updates have revised the pulse-count tolerance window to reduce false P0371 flags caused by minor noise. Check for applicable TSBs before replacing hardware — if there is a known calibration fix from the OEM, applying it first may resolve the code without any physical repair.
Disabling P0371 in software
RaceTune can permanently disable P0371 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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