P0385
Crankshaft Position Sensor B Circuit Malfunction
When a vehicle powertrain module registers the fault code P0385, it points directly to an internal system malfunction identified as "Crankshaft Position Sensor B Circuit Malfunction". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
Code P0385 means your vehicle detected a problem with the crankshaft position sensor b circuit malfunction system. On the road, this usually shows up as hard starting, stalling, poor engine performance. Stop driving as soon as it is safe to do so. This fault can lead to expensive secondary damage if left unaddressed.
Symptoms
Hard starting, stalling, poor engine performance
Common Causes
- Failed crankshaft position sensor B
- Damaged wiring harness
- Corroded electrical connector
- Defective PCM
How to Fix
- 1 Replace crankshaft position sensor B
- 2 Repair wiring harness
- 3 Clean electrical connector
- 4 Test and replace PCM
Technical Explanation
The PCM triggers P0385 after its internal monitoring routine detects that a specific circuit or sensor has exceeded its acceptable operating range. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including failed crankshaft position sensor b — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
Module replacement should always be the last resort for P0385 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Sensor replacement: 150 - 350