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.
- 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
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.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Check for RPM signal on scan tool during cranking. No RPM = no crank sensor signal.
-
Inspect crank sensor connector and wiring.
-
Measure crank sensor resistance (varies by type: 200-2000 ohms for magnetic, check spec for Hall effect).
-
Verify reluctor wheel is intact and rotating with the crankshaft.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- 2010-2020 Ford F-150 (3.5L EcoBoost)
- 2012-2019 Toyota Camry (2.5L)
- 2008-2018 Chevrolet Silverado (5.3L)
- 2011-2020 Honda CR-V (1.5T)
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