Faulty crankshaft position sensor B; Damaged, chafed or corroded wiring, or a poor connector, in the sensor signal, supply or earth circuit; Contamination, metal debris or an incorrect air gap between the sensor and the reluctor ring; Damaged or dirty reluctor wheel or trigger ring, or a loose or slipped component carrying it; Low battery voltage or a weak supply or earth affecting the sensor reference; Incorrect timing between the crankshaft and camshaft after a belt or chain fault; Fault within the engine control unit.

P0385

Crankshaft Position Sensor B Circuit.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
85: FaultThe specific fault in that area

What it means

P0385 means the engine control unit has detected a fault in the circuit of crankshaft position sensor 'B', which is a second crankshaft sensor or a secondary signal circuit. The fault is set when the signal is missing, erratic, out of range or implausible compared with other inputs, such as the camshaft sensor. Which sensor is 'B' and how the fault is detected depends on the vehicle and engine.

Symptoms

Engine cranks but fails to start or is hard to start
Engine stalls unexpectedly or cuts out while driving
Misfire, rough running or hesitation
Rev counter flickering, dropping to zero or not working
Engine management light on, possibly with limp mode
Intermittent starting problems that may worsen when hot

Possible causes

Faulty crankshaft position sensor Blikely
Damaged, chafed or corroded wiring, or a poor connector, in the sensor signal, supply or earth circuitlikely
Contamination, metal debris or an incorrect air gap between the sensor and the reluctor ringpossible
Damaged or dirty reluctor wheel or trigger ring, or a loose or slipped component carrying itpossible
Low battery voltage or a weak supply or earth affecting the sensor referencepossible
Incorrect timing between the crankshaft and camshaft after a belt or chain faultrare
Fault within the engine control unitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine speed, temperature and battery voltage
Check for related codes, such as other crankshaft or camshaft sensor faults, and clear and retest to see if P0385 returns
Inspect the sensor, its wiring and connector for damage, heat, oil, water ingress, chafing and corrosion
Check the battery condition and charging voltage, as low voltage can cause false signal faults
Look at live engine speed data while cranking to see whether a signal is present and stable
Test the sensor supply, earth and signal circuits against the manufacturer's data, including continuity and shorts
Remove the sensor to check for debris, damage and the condition of the reluctor ring, and confirm correct fitting and air gap
Compare the crankshaft and camshaft signals on a scope, and check mechanical timing if the signals are out of step

How to fix

Replace the crankshaft position sensor if it fails testing, using the correct type for the engine
Repair or replace damaged wiring and clean or renew corroded or loose connectors
Clean the sensor mounting area and correct the fitting or air gap where the design allows
Replace a damaged or faulty reluctor ring, or repair the mechanical fault that affects it
Restore battery and charging system health if voltage is low
Correct the engine timing if it is incorrect, or repair or replace the control unit only after all other causes are ruled out

Can I keep driving?

High severity

Avoid driving, as the engine may stall without warning, which risks loss of power assistance and an unsafe situation in traffic. If the car starts and runs normally, limit driving to getting it to a workshop.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.