Crankshaft Position Sensor B Circuit
The P0385 code means the vehicle's onboard diagnostic system has detected: Crankshaft Position Sensor B Circuit. This is a critical severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- moderate
- Estimated cost
- $80 - $400 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Engine may not start
- Engine stalls
- Erratic RPM readings
Probable Causes (Ranked by Likelihood)
- Faulty crankshaft position sensor B Very High
- Damaged wiring to crank sensor B High
- Corroded sensor connector Moderate
- PCM input circuit fault Low
Frequently Asked Questions
What is crankshaft position sensor B?
Sensor B is a secondary or backup crankshaft position sensor. Some engines use two sensors for redundancy or to measure different aspects of crankshaft rotation.
Why does my engine have two crank sensors?
Dual crank sensors provide redundancy for safety and can measure crankshaft acceleration (knock detection) in addition to position.
Is P0385 always a no-start?
Not always. If sensor A is working, the engine may run with reduced performance using only one crank sensor signal.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Check for RPM signal from sensor B on scan tool.
-
Measure sensor B resistance and compare to spec.
-
Inspect connector and wiring for damage.
-
Test signal output with oscilloscope.
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-250 (6.7L Diesel)
- 2012-2019 Chevrolet Silverado 2500 (6.6L Duramax)
- 2008-2018 Ram 2500 (6.7L Cummins)
- 2011-2020 Toyota Tundra (5.7L V8)
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