What does it mean?
This diagnostic code (DTC) is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996 and newer), although specific repair steps may vary slightly by model.
The crankshaft position sensor (CKP) is typically a two-wire sensor: one signal and one ground. The CKP sensor usually consists of a permanent magnet sensor mounted in front of a reluctor wheel (toothed) attached to the crankshaft.
As the reluctor wheel passes by the crank sensor, an A/C signal is produced that varies with engine speed. The PCM (Powertrain Control Module) uses this A/C signal to interpret engine RPM. Some crank sensors are Hall effect sensors instead of permanent magnet sensors. These are three-wire sensors, with power, ground, and signal wires. They also have a reluctor wheel with blades and “windows” that change the voltage signal to the PCM, providing an RPM signal. I will focus on the former, as they are simpler in design and more common.
The crankshaft reluctor has a specific number of teeth, and the PCM can determine the crankshaft position using only the signature pattern from this sensor. The PCM also uses this sensor to determine cylinder misfires by measuring the positions of the reluctor teeth in the CKP sensor signal. In conjunction with the camshaft position sensor (CMP), the PCM can determine the timing for spark and fuel injection. If the PCM detects a loss of signal from the CKP sensor (RPM signal) even momentarily, P0386 may set.
Note: This DTC refers to the “B” sensor. Refer to a vehicle-specific repair manual to confirm the location of your “B” crankshaft position sensor. In the case of some GM (Cadillac) engines, the “B” sensor is the upper one while the “A” sensor is the lower one, but check to be sure. This code is essentially the same as P0336 but refers to the “B” sensor.
Related Crankshaft Position B Sensor Fault Codes:
P0385 Crankshaft Position B Sensor Circuit Malfunction
P0387 Crankshaft Position B Sensor Circuit Low Input
P0388 Crankshaft Position B Sensor Circuit High Input
P0389 Crankshaft Position B Sensor Circuit Intermittent
Symptoms
Symptoms of a P0386 DTC may include:
Intermittent stalling and no start
No start
MIL (Malfunction Indicator Lamp) illumination
Intermittent misfires
Causes
Potential causes of a P0386 code include:
Faulty crank sensor
Damaged reluctor ring (missing teeth, debris lodged in the ring)
Reluctor ring dislodged/stripped from its fixed position
Chafing of the wiring harness causing a short circuit
Open wiring in the CKP circuit
Possible Solutions
Crankshaft sensor issues are sometimes intermittent, and the vehicle may start and run for a while until the problem occurs. Try to replicate the complaint. When the engine stalls or if the engine does not start and keeps cranking, start the engine while observing the RPM reading. If there is no RPM reading, check if a signal is coming from the crank sensor. It is best to use an oscilloscope, but since most DIYers do not have access to one, you can use a code reader or the tachometer to check the RPM signal.
Visually inspect the CKP harness for any damage or cracks in the wiring insulation. Repair as needed. Ensure the wiring is not improperly routed near high-tension spark plug wires. Check for any loose connections or broken locks at the sensor connector. Repair as needed. Obtain a resistance specification for the crank sensor. Remove it and test it. If it fails, replace it. If it checks out, inspect the reluctor ring for damage, broken teeth, or debris lodged in the ring. Make sure the reluctor ring is not dislodged. It must be stationary on the crankshaft. Carefully repair/replace as needed. Note: Some reluctor rings are located in the transmission bell housing or behind the front engine cover and are not easily accessible.
If the vehicle stalls intermittently and after stalling, you have no RPM signal and you have verified that the CKP sensor wiring is good, try replacing the sensor. If that does not take care of it and you cannot access the reluctor ring, seek assistance from an automotive professional.