P0385 - Crankshaft Position Sensor B Circuit Malfunction
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0385 indicates that the Engine Control Unit (ECU) has detected an incorrect signal or a lack of signal from the secondary crankshaft position sensor (Sensor B). The crankshaft sensor is critical for determining exact engine position and rotational speed (RPM). The system typically uses a Hall-effect or inductive sensor reading a tone wheel. The ECU logic requires a stable square wave or sine wave; if the signal is interrupted, noisy, or outside expected voltage thresholds, the code is set. This directly affects fuel injection timing and ignition spark.
Possible Causes
Faulty crankshaft position sensor (Sensor B)
Damaged wiring harness or short circuit in the sensor wiring
Defective reluctor ring (damaged teeth or debris)
Internal ECU fault or improperly installed sensor
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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