OBD-II Trouble Code Description for P0385 GMC

Crankshaft Position Sensor “B” Circuit

What does this mean?

OBD2 Code P0385 GM definition:
The crankshaft position sensor (CKP) measures crankshaft location and relays this information to the PCM (Powertrain Control Module). Depending on the vehicle, the PCM uses this crankshaft position information to time the spark properly or on some systems it is only for misfire detection and does not control spark timing. The CKP sensor is stationary and works in harmony with a reluctor ring (or toothed ring) that is attached to the crankshaft. As this reluctor ring passes in front of the CKP sensor, the magnetic field created by the CKP sensor is interrupted and this creates a square wave voltage signal that the PCM interprets as crankshaft position. If the PCM detects that there are no crankshaft pulses or if it sees a problem with the pulses on the output circuit, P0385 GM will set.

Symptoms

Possible sumptoms of OBD code P0385 GM
NOTE: If the crank sensor is used only for misfire detection and NOT spark timing (this varies with the vehicle), the vehicle should start and run with MIL (Malfunction indicator lamp) illumination. Also, some vehicles require several key cycles to illuminate the MIL. If this is the case, there may be no MIL illumination until the problem often enough over time. If the crank sensor is used for BOTH misfire detection and spark timing, the vehicle may or may not start. Symptoms may include: Vehicle may not start (see above) Vehicle may run rough or misfire MIL illumination

Causes

Possible causes of OBD code P0385 GM
Damaged CKP sensor connector Damaged reluctor ring (missing teeth or not turning due to sheared-off keyway) Sensor output open Sensor output shorted to ground Sensor output shorted to voltage Failed crank sensor Failed PCM

Possible Solutions

Using a scan tool, check if, when engine is running or cranking, that there is an RPM signal. If there is no RPM reading, then visually inspect the crank Sensor Bnd connector for any damage and repair as necessary. If there is no visible damage, and you have access to a scope, you could check the CKP 5 Volt square wave pattern. If you do not, then, obtain a resistance reading of your crank sensor from a repair manual. (There are so many different types of crank sensors that there’s no way to put here which resistance reading is correct). Then check the resistance of the CKP sensor by disconnecting the Sensor Bnd measuring resistance of the sensor. (It is best to check resistance readings from the PCM connector. This rules out any wiring problems from the start. But it does require some mechanical skill and shouldn’t be performed if you’re not familiar with automobile electrical systems). Is the sensor within resistance specs? If not, replace the CKP sensor. If so, recheck resistance reading from the PCM connector. Is the reading still okay? If not, repair open or short in the wiring to the crank Sensor Bnd re-check. If the reading is okay, the problem is intermittent or the PCM may be at fault. Try reconnecting and checking for RPM signal again. If there is now an RPM signal, wiggle test the wiring harness to try and induce the fault.

Related Codes

P0335 GM P0335 GM P0385 GM P0016 GM P0017 GM P0018 GM P0019 GM P0335 GM P0336 GM P0337 GM P0338 GM P0339 GM P0385 GM P0386 GM P0387 GM P0388 GM P0389 GM