Knock sensor replacement
The knock sensor detects micro-detonations in the cylinders and lets the control unit reduce ignition advance in time.
Symptoms
- The engine loses power and burns more fuel from permanently retarded ignition timing.
What's included
- Its failure can lead to two scenarios: the control unit keeps ignition retarded, so the engine loses power and uses more fuel, or detonation goes unnoticed, which can burn through pistons. We check the sensor signal and always control the tightening torque during installation: this sensor is sensitive to clamping force, and it will work incorrectly when over- or under-tightened even if it is new. After replacement, we check ignition advance in live data under load.
Additional checks
- Knock sensor signal
- Sensor tightening torque during installation
- Ignition advance in live data under load (after replacement)
Why it matters
The other scenario is worse: unnoticed knock leads to burnt pistons. The sensor is sensitive to tightening torque — over- or under-tightened, it misbehaves even when new.
More details
The knock sensor detects micro-explosions in the cylinders and lets the control unit retard the ignition timing in time. When it fails, two scenarios are possible: either the control unit permanently keeps the timing retarded, so the engine loses power and burns more fuel, or knock goes undetected — a direct path to burned pistons. We check the sensor's signal and always check the tightening torque during installation: this sensor is sensitive to mounting force, and if it's over- or under-tightened it works incorrectly even when brand new. After replacement we check the ignition timing in the live data under load.
Need a Technician Consultation?
Describe the vehicle and symptoms, and we will suggest which check to start with.
Book a Diagnostic