Timing Reference High Resolution Signal B Pulse Width Not Within Expected Range
The P0377 code means the vehicle's onboard diagnostic system has detected: Timing Reference High Resolution Signal B Pulse Width Not Within Expected Range. This is a critical severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- hard
- Estimated cost
- $100 - $700 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Engine performance degraded
- Possible misfires
- Timing-related issues
Probable Causes (Ranked by Likelihood)
- Worn or damaged camshaft reluctor wheel Very High
- Incorrect camshaft sensor air gap High
- Failing camshaft position sensor Moderate
- Timing chain stretch altering pulse width Low
Frequently Asked Questions
What is pulse width in timing signals?
Pulse width is the duration of each signal pulse from the reluctor wheel. If teeth are worn or the gap is wrong, pulse width will be outside spec.
Can this indicate timing chain problems?
Yes, a stretched timing chain changes the relationship between crankshaft and camshaft positions, which alters pulse width timing.
Is P0377 a common code?
No, P0377 is uncommon and indicates a subtle issue with the cam sensor signal quality rather than a complete failure.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Compare cam sensor pulse width on oscilloscope to specification.
-
Check sensor air gap with feeler gauge.
-
Inspect reluctor teeth for wear or damage.
-
Check timing chain for stretch.
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 Chevrolet Silverado (5.3L)
- 2008-2018 Toyota Camry (2.5L)
- 2011-2020 Honda CR-V (1.5T)
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