P0328
PowertrainKnock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
Most people first notice this when the engine warning light comes on and the car feels a bit flat, like it's lost some of its eagerness when you put your foot down. What's happening is the ECU sees the voltage coming back from the knock sensor on Bank 1 sitting higher than it should, outside the range it expects to see. That usually points to a wiring or sensor fault in the circuit rather than the engine actually pinking. Because the ECU can't trust the sensor, it pulls back ignition timing to play it safe, and that's what robs you of power and a bit of economy.
ⓘ Information only. This page provides general educational information about fault code P0328. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0328 mean?
P0328 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor).
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on the dash, frequently the first and only thing you'll notice
- • Sluggish acceleration, especially when the engine is under load going up a hill or pulling away
- • Fuel consumption creeping up because the ECU is running conservative timing to protect the engine
- • On some cars the engine runs warmer than usual
- • Rough idle or a slight hesitation when you accelerate
- • An actual knocking or pinging from the engine bay, though that's less common with this code and usually means a separate mechanical problem worth chasing
Possible causes
Causes commonly associated with P0328, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Faulty knock sensor, often a cracked ceramic element or an internal short that throws the voltage high
- 2. Wiring fault in the sensor circuit, typically a short to voltage or a broken wire somewhere in the loom
- 3. Corroded or loose connector at the sensor or the ECU end, very common on older cars where moisture has got in
- 4. Poor sensor ground or a loose mounting, since these sensors are torque-sensitive and the wrong tightness messes with the signal
- 5. Electrical interference from a nearby component bleeding into the circuit
- 6. ECM or PCM input circuit fault, where the module itself isn't processing the signal correctly. Rare, but it happens
- 7. Genuine engine knock from poor fuel octane, overheating or a mechanical issue, though this is the least likely cause behind a high-input code specifically
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Pull the freeze frame data with the code and note the engine speed, load, temperature and voltage at the moment it logged. That tells you whether the fault is constant or only shows up under certain conditions
- 2. Get eyes on the sensor, the harness and the connector. Look for chafed wires, green corrosion in the plug, or a connector that isn't seated. This is where the cheap fixes live
- 3. Measure resistance and voltage at the sensor terminals with a multimeter and compare against the manual values for that engine
- 4. Check continuity in the wiring between the sensor connector and the ECU, hunting for an open circuit or a short to voltage
- 5. Confirm the sensor is mounted to the block at the correct torque and sitting flush, because a loose sensor reads erratically
- 6. If the circuit and sensor all check out clean, then look at the ECU input side or a calibration update before condemning the module
Common questions about P0328
How long is this likely to take to sort? +
If it turns out to be a duff connector or a chafed wire, a competent garage can find and fix it inside an hour. A sensor swap on an inline four where the part is reachable is usually under an hour of labour too. The pain comes on V-configuration engines where the sensor sits beneath the inlet manifold, because that's typically a two to three hour job once you factor in removing the manifold and fitting fresh gaskets on the way back.
Should I fit a cheap aftermarket sensor or pay for a genuine one? +
A decent mid-range aftermarket knock sensor from a known brand like Bosch or NTK does the job perfectly well and costs a good bit less than the dealer part. Where I'd steer clear is the £8 no-name listings, because these sensors are piezoelectric and the cheap ones can read out of spec or fail within months, which is no fun if it's buried under your manifold. Buy something reputable and you won't be doing the job twice.
Is it OK to carry on driving like this? +
Short trips to get home or to the garage won't wreck anything. The car has gone into a protective state and pulled timing back, which is exactly what it's meant to do, so you'll feel down on power and burn a touch more fuel. The risk is if there's real knock going on underneath, because driving hard on retarded timing for weeks can wear the engine. Get it looked at soon rather than ignoring the light for months.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →