Crankshaft Position Sensor B Circuit High
The P0388 code means the vehicle's onboard diagnostic system has detected: Crankshaft Position Sensor B Circuit High. This is a critical severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- moderate
- Estimated cost
- $80 - $400 (parts and labor)
Best-selling code reader on Amazon. Reads and clears check engine codes on any 1996+ vehicle. Under $30.
Essential for diagnosing sensor codes, checking voltage, and testing circuits. Under $15 and pays for itself on the first job.
Affiliate links — we earn a commission at no extra cost to you.
Common Symptoms
- Check Engine Light on
- Engine may not start
- Stalling
- No signal from sensor B
Probable Causes (Ranked by Likelihood)
- Open circuit in crank sensor B wiring Very High
- Failed sensor (open) High
- Disconnected connector Moderate
- PCM input open Low
Frequently Asked Questions
What does circuit high mean on crank sensor B?
An open circuit or disconnected sensor causes the signal voltage to float high.
Can I just use sensor A?
Some engines can run on one crank sensor in degraded mode, but it is not reliable for long-term operation.
How long does crank sensor replacement take?
Typically 30-60 minutes for sensor replacement, depending on accessibility.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Check connector is seated.
-
Measure sensor resistance.
-
Test wiring continuity.
-
Replace sensor if wiring is intact.
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 Ram 3500 (6.7L Cummins)
- 2012-2019 Ford F-350 (6.7L Diesel)
- 2008-2018 GMC Sierra 3500 (6.6L Duramax)
- 2011-2020 Chevrolet Silverado 3500 (6.6L Duramax)
Related Codes
Explore More
Was this helpful?
Send this to whoever is fixing the car — your mechanic, or the person asking what the light means.