What does it mean?
P1333 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Knock Sensor 4 Signal High Input .
Symptoms
- Check engine light on, with the code often setting during acceleration or under sustained load
- Continuous ignition retard, giving a soft, unresponsive engine
- Noticeably higher fuel consumption on hills and while towing
- Slight roughness or vibration in the mid rpm band on some engines
- Additional bank-related codes may appear alongside this one
Likely causes
- Short to voltage in the sensor signal circuit, often where the harness passes ignition coils or a heated connector
- Over-tightened sensor or a distorted mounting boss, which pre-loads the piezo element and raises output
- Damaged or ungrounded shielding, letting electrical interference ride on the signal
- Internal short inside knock sensor 4
- Mechanical noise close to the sensor, such as a loose heat shield, a worn tensioner or an injector that ticks louder than normal
- Corroded module ground, which shifts the reference and makes every sample look high
- Failed knock input in the control module
How to fix it
- Check the freeze frame for the rpm and load window, then decide whether the pattern points to interference or a failed sensor
- Inspect the harness for melted insulation and reroute it away from ignition components
- Test the signal circuit for the presence of voltage with the sensor unplugged and the key on, which exposes a short to power
- Compare the live output of knock sensor 4 with the other sensors at idle; a channel that never drops is the suspect
- Verify the module and shield grounds are clean, tight and free of corrosion
- Retorque the sensor on a clean surface to specification and recheck, since incorrect torque alone can set this fault
- Replace knock sensor 4 if the high level follows the sensor rather than the wiring