P1332
Knock Sensor 4 Low Input.
- BMW
- Powertrain
- Manufacturer code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 3
- AreaIgnition system or misfire
- 32
- FaultThe specific fault in that area
What it means
P1332 on a BMW means the engine control unit has seen a signal from knock sensor 4 that is too low or absent, so it cannot trust that sensor to detect combustion knock. Knock sensors produce a small voltage when the block vibrates, and the control unit expects a signal within a plausible range. Which cylinders sensor 4 covers and where it sits depends on the engine, so check the workshop data for the specific model.
Symptoms
- Engine warning light on
- Reduced power or flat feeling under load
- Higher fuel consumption
- Rough running or hesitation when accelerating
- Possible audible pinking under load if the control unit has to retard timing for safety
Possible causes
- Damaged, chafed or oil-soaked wiring to knock sensor 4likely
- Corroded, loose or contaminated connector at the sensor or control unitlikely
- Failed knock sensor 4likely
- Sensor loose or incorrectly torqued, giving a weak signalpossible
- Short to earth or open circuit in the signal or shielding wirepossible
- Fault inside the engine control unitrare
How to diagnose
- Read all stored and pending codes and record the freeze frame data, noting any other knock sensor or misfire codes.
- Identify the location of knock sensor 4 for this engine from the workshop data, as it varies by engine and may sit under other components.
- Inspect the harness and connector for chafing, heat damage, oil contamination, corrosion and bent or pushed-back pins.
- Check the sensor is fitted correctly and tightened to the specified torque, and that its mounting face is clean.
- With the connector unplugged, test the signal wire and shielding for continuity, short to earth and short to supply, using the wiring diagram.
- Test the sensor against the manufacturer's specification, or view its signal on a diagnostic scope while tapping the block lightly near the sensor.
- Clear the code and road test, then recheck for the fault returning and review live knock data.
How to fix
- Repair or replace the damaged section of wiring, using proper soldered and sealed repairs or a new harness section as the workshop data allows.
- Clean or replace a corroded or damaged connector and its terminals.
- Replace the faulty knock sensor and tighten it to the specified torque.
- Correct the sensor mounting if it was loose, and clean the mating surface.
- Fix any oil or coolant leak that is contaminating the harness or connector.
- Only after all else is ruled out, diagnose and replace or repair the control unit as the manufacturer advises.
Can I keep driving?
Medium severity
The car can usually be driven gently for a short time, but avoid heavy load, high revs and towing. Without a working knock sensor the control unit cannot protect the engine properly, so have it fixed soon.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.