Knock Sensor: Testing and Inspection

Knock Sensor, Checking

NOTE:
- it is extremely important to keep to the tightening torque of 20 Nm to ensure the knock sensors perform perfectly.
- Only gold-plated contacts may be used when servicing the knock sensor connector contacts.


Special tools and workshop equipment, testers, measuring instruments and auxiliary items required

- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram

Test conditions
- On Board Diagnostic (OBD) must have recognized a fault on one or both knock sensors.

Checking resistances and wiring







- Separate 3 pin connector to knock sensor 1 (G61) -1-.
- Measure resistance between the contacts 1+2, 1+3 and 2+3 at connections to knock sensors.
Specification infinity ohms







- Separate 3 pin connector to knock sensor 2 (G66) -1-.
- Measure resistance between the contacts 1+2, 1+3 and 2+3 at connections to knock sensors.
Specification infinity ohms

If the specification is not obtained:
- Replace knock sensor(s)

If the specification is obtained:







- Connect test box VAG 1598/31 to control module wiring harness. The engine control module remains disconnected.
- Check wiring between test box and 3- pin connector for open circuit using wiring diagram.

G61: G66:

Contact 1 + socket 106 107
Contact 2 + socket 99 99
Contact 3 + socket 108 108

Wire resistance: Max. 1.5 ohms

- Additionally check wires for short to one another.

If no wiring fault is detected:
- Loosen knock sensor and tighten again to 20 Nm.
- Carry out test drive.

During the road test the following operating conditions must be fulfilled:
- The coolant temperature must exceed 80 °C.
- When the temperature is reached, the operating conditions
Idling
Part throttle
Full throttle
Overrun
must be attained several times.
- At full throttle the speed must exceed 3500 RPM.
- Again interrogate the control module fault memory.

If the fault is still present:
- Replace knock sensor(s)