What does it mean?
P1385 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Knock Sensor 4 Circuit Malfunction .
Symptoms
- MIL on with the code stored
- Noticeably weaker acceleration because the module retards timing to protect the engine
- Knocking or pinging under heavy load, especially with lower octane fuel
- Mild increase in fuel consumption
- No obvious change at idle, the fault mainly shows under load
Likely causes
- Broken or shorted signal wire in the knock sensor 4 circuit
- Water, oil or coolant inside the sensor connector
- Sensor loose on the block or a washer fitted where none belongs
- Internal failure of the sensor element
- Shield ground open, allowing injector and alternator noise onto the signal line
- Harness routed against a sharp bracket and worn through
- Control module input circuit failure
How to fix it
- Look at the knock sensor 4 signal in live data alongside the other sensors while revving the engine
- Remove the connector, inspect for corrosion and dry it properly if wet
- Measure sensor resistance and check that it is not shorted to the block
- Test the wiring for continuity and for shorts along its full length to the module
- Clean the mounting boss, refit the sensor at the correct torque with no washer
- Replace the sensor if it stays electrically dead
- Clear the code, road test under load and confirm normal timing advance returns