P0327 and P0332: knock sensor circuit low on bank 1 and 2

Detonation — fuel igniting from pressure rather than from the spark — destroys pistons and bearings quickly. The knock sensor is a piezoelectric microphone bolted to the engine block, listening for the specific frequency that detonation produces.

When the ECU stops receiving a plausible signal from it, it has to assume the worst.

Code	Meaning
P0325	Knock sensor 1 circuit malfunction, bank 1
P0327	Circuit low input, bank 1
P0328	Circuit high input, bank 1
P0330	Knock sensor 2 circuit malfunction, bank 2
P0332	Circuit low input, bank 2

Background: knock sensor diagnostics P0325.

The symptom is power you never notice losing

Without a working knock sensor, the ECU cannot tell whether the engine is detonating. Its safe response is to run conservative ignition timing all the time.

The result is subtle: slightly less power, slightly worse fuel consumption, a car that feels flat but has nothing obviously wrong. Many owners drive for months without connecting it to the warning lamp.

Check ignition advance under load in the live data. Timing that never advances beyond a modest figure at full throttle is a car in protection mode.

The torque specification actually matters

This is the part that catches people out on repairs.

A knock sensor works by mechanical contact with the block. It must be torqued to a specific figure — too loose and it cannot hear the engine, too tight and its response changes. There is usually no washer, and the mating face must be clean.

A sensor replaced without a torque wrench frequently sets the same code again. If a workshop replaced yours and the code returned, this is the first thing to question.

Causes

Wiring and connector

The most common cause of a circuit-low code. These sensors sit low on the block, often under the intake manifold, in the path of heat and oil.

The cable is shielded, and the shield matters — this is a low-level signal in an electrically noisy environment. Repairs made by twisting wires together produce intermittent faults.

The sensor itself

Piezoelectric elements degrade with heat cycling. Failure is usually gradual: reduced sensitivity first, then an out-of-range signal.

Corrosion at the connector

Particularly where the connector sits in the engine valley and collects debris.

Genuine detonation

Worth stating: if the engine really is knocking, that is a mechanical and fuel problem, not a sensor problem. Causes include poor fuel, carbon deposits raising compression, overheating, or a lean mixture.

Engine knocking noise diagnosis and bad fuel quality OBD symptoms.

Bank 1 versus bank 2

On a V-engine with two sensors, which bank has the code narrows the search to one side of the engine immediately.

If both banks show codes at once, suspect something shared — a common ground, the connector on a shared harness branch, or the ECU input — rather than two sensors failing on the same day.

Access is the real cost

On many engines the knock sensor sits under the intake manifold. The part is inexpensive; the labour to reach it is not.

That makes diagnosis worth doing properly. Confirm the wiring and the connector before committing to the job, because removing an intake manifold to fit a sensor that was never faulty is an expensive way to learn.

DIY vs workshop: what to attempt.

What to check in the data

• Ignition timing advance under load. Conservative timing that never advances confirms protection mode.
• Knock retard or knock correction, where the vehicle exposes it. A value pegged at maximum retard is the ECU compensating.
• Fuel trims, because a lean condition causes genuine knock: P0171 and P0174 lean mixture.
• Coolant temperature, because an engine running hot detonates more readily.

In what order

1. Read all codes. Both banks affected changes the search.
2. Check ignition advance under load to confirm the performance impact.
3. Inspect the connector and harness for heat and oil damage.
4. Check whether the engine is genuinely knocking — fuel quality, temperature, mixture.
5. Replace the sensor with correct torque if the wiring is sound.
6. Confirm timing advance returns after the repair.

That last step is the one people skip, and it is the proof the repair worked.

This check needs no workshop — an ELM327 adapter and the free tier of the app cover it. Log ignition advance through a full-throttle pull. A car with a dead knock sensor is measurably down on timing, and that measurement is the evidence.