What it means
The knock or combustion-vibration sensor monitors the structure-borne noise of each cylinder. The signal level for cylinder 12 has stayed above the diagnostic threshold for an extended period, indicating either persistent knock or an electrical fault that biases the channel high.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module uses knock or combustion-vibration signals associated with cylinder 12 to detect abnormal combustion. This code sets when the cylinder 12 signal remains above its calibrated threshold long enough to indicate persistent knock or a signal biased high by a sensor, wiring, or message-routing fault.
Common causes
Most likely first.
- Persistent knocking on cylinder 12
- Sensor or wiring biased high
- Gateway module routing CAN messages incorrectly
Symptoms
- Check-engine light
- Pinging or rattling under acceleration
- Reduced power or sluggish acceleration
How to diagnose it
- Save freeze-frame data and review live knock or vibration data for cylinder 12 to see when the signal rises and whether it tracks engine load.
- Listen for pinging under acceleration and check fuel quality, since real knock on cylinder 12 can raise the signal.
- Inspect the cylinder 12 sensor connections and harness for loose, damaged, or shorted wiring that could bias the signal high.
- Compare cylinder 12 data with other cylinders and check the sensor circuit according to the manufacturer's procedure.
- If the cylinder 12 signal is implausible despite sound wiring, check relevant gateway or control-module communications for routing faults.
Common fixes
- Correct poor-quality or unsuitable fuel if it is contributing to knock.
- Repair damaged or poorly connected cylinder 12 sensor wiring or terminals.
- Replace a cylinder 12 knock or vibration sensor shown to be biased high by testing.
- Diagnose and repair a confirmed gateway or module communication-routing fault.
Can I keep driving?
Avoid hard acceleration if the engine pings or loses power; sustained knock can damage the engine. If the noise is pronounced or power drops sharply, stop driving and have the fault assessed.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.