Code
P0385
GWM
P — Powertrain
- Malfunction in the sensor circuit B of the crankshaft position
AI status
Completed
Completed
100%
Causes
- Faulty crankshaft position sensor B
- Open, short or intermittent wiring in sensor B circuit
- Corroded/damaged connector or poor pin contact
- Damaged or missing teeth on reluctor/tone ring (wheel)
- Contaminated sensor (oil/debris), misaligned sensor air gap
- Faulty PCM or poor PCM ground/reference (less common)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated (check engine light)
- Engine cranks but may not start, or intermittent no‑start
- Rough idle, misfire or hesitation under load
- Reduced engine performance or limp mode in some vehicles
- Stalling or poor acceleration; erratic RPM signal on scan tool
What to check
- Read and record freeze‑frame data and all stored codes with a scan tool
- Confirm code is current (erase and reproduce if necessary)
- Inspect CKP B connector, wiring harness and chassis/PCM grounds for damage or corrosion
- Compare live CKP B signal to CKP A (if present) using a scope or scan tool
- Visually inspect reluctor/tone wheel and sensor mounting for damage, missing teeth, or excessive gap
- Check reference voltage and ground at the sensor connector (with ignition ON)
Signal parameters
- Hall‑effect (3‑wire): 5V reference, ground, and square‑wave signal 0–5V; frequency varies with engine speed
- Variable reluctance (VR, 2‑wire): AC sine signal; amplitude increases with RPM (hundreds of mV to several volts)
- Typical sensor resistance varies by design (consult service data) — open or shorted reading indicates failure
- Expected waveform: clean repetitive pulses matching crankshaft teeth; missing or distorted pulses indicate mechanical or electrical fault
Diagnostic algorithm
- Connect scan tool, read codes and live data; confirm P0385 is active and note freeze frame conditions
- Visually inspect CKP B connector, wiring along harness to PCM, and sensor mounting for damage, corrosion, loose pins or oil contamination
- With ignition OFF, wiggle harness and connector while monitoring for intermittent faults (may require oscilloscope or backprobe and assistant)
- Check sensor reference voltage and ground at the connector with ignition ON (for Hall sensors ~5V ref; for VR sensors check continuity to PCM ground)
- Measure sensor output: use oscilloscope to view waveform while cranking/idle; for VR sensor measure AC volts while cranking; for Hall sensor verify square wave 0–5V
- If sensor output absent or abnormal, measure sensor resistance (if specified) and compare to factory spec; replace sensor if out of spec
- If sensor tests good but signal still absent, backprobe harness to check for open/short to power or ground, and pin‑to‑pin continuity to PCM; repair wiring/connector as needed
- Inspect reluctor/tone ring for missing/damaged teeth, correct mounting and alignment; repair or replace damaged wheel or timing component if required
- After repair, clear codes, perform test drive and verify CKP B signal and that P0385 does not return; recheck freeze frame data if necessary
- If wiring and sensor verify good but problem persists, test PCM input for the CKP B circuit or consult manufacturer service data for specific PCM diagnostics
Likely causes
- Wiring harness chafed or connector corroded at CKP B
- Failed CKP sensor B (internal electronics or magnet)
- Reluctor/tone ring damaged, loose or missing tooth near sensor B
- Connector pin pushed out or water ingress in connector
- Short to power or ground in signal/reference circuit
Fault status
Status
Malfunction in crankshaft position sensor B circuit — signal missing, intermittent, out of expected range, or faulty reference/ground.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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