P0371 critical

Timing Reference High Resolution Signal A No Pulses

The P0371 code means the vehicle's onboard diagnostic system has detected: Timing Reference High Resolution Signal A No Pulses. This is a critical severity code.

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Keep driving?
No -- stop driving
DIY difficulty
hard
Estimated cost
$100 - $600 (parts and labor)
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Common Symptoms

  • Engine cranks but will not start
  • Check Engine Light on
  • No RPM reading on scan tool during cranking
  • No tachometer reading

Probable Causes (Ranked by Likelihood)

  • Failed crankshaft position sensor Very High
  • Broken or disconnected crank sensor wiring High
  • Sheared reluctor wheel key Moderate
  • PCM crank sensor input circuit failure Low

Step-by-Step Diagnostic Procedure

  1. Check for RPM signal on scan tool during cranking. No RPM = no crank sensor signal.

  2. Inspect crank sensor connector and wiring.

  3. Measure crank sensor resistance (varies by type: 200-2000 ohms for magnetic, check spec for Hall effect).

  4. Verify reluctor wheel is intact and rotating with the crankshaft.

Frequently Asked Questions

Why does the engine crank but not start?

Without a crankshaft position signal, the PCM cannot determine engine position and will not fire the ignition coils or fuel injectors.

Is this always the crank sensor?

Usually yes, but a sheared keyway on the reluctor wheel or a broken trigger plate can also cause no-signal conditions.

How do I test a crank sensor quickly?

The fastest method is to check for RPM on a scan tool while cranking. If there is no RPM reading, the crank sensor or its circuit has failed.

Sources

This page is built from documented references. Verify against your own service info before repair work.

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