Knock Sensor: Testing and Inspection

Knock Sensor, Checking

This procedure is used to diagnose Knock Sensor (KS) 1 (G61) and Knock Sensor (KS) 2 (G66).

Special tools, testers and auxiliary items required

• Multimeter

• wiring diagram

• Cylinders 1, 2 are monitored by Knock sensor (KS) 1 (-G61-). Cylinders 3,4 are monitored by Knock sensor (KS) 2 (-G66-).

• Knock sensors themselves cannot be checked electrically.

• When servicing terminals in the harness connector of knock sensors, use only gold-plated terminals.

• For the knock sensors to function properly, it is important that the tightening torque be exactly 20 Nm.

• Contact surfaces between Knock Sensor (KS) 1 (G61 ) and Knock Sensor (KS) 2 (G66) and cylinder block must be free of corrosion, dirt and grease.

Test requirements

• Mounting bolt of Knock Sensor (KS) 1 (G61)/Knock Sensor (KS) 2 (G66) tightened to 20 Nm.

• Fuses for Engine Control Module (ECM) (J623) OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, shift selector lever into position " P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

- Pull engine cover out of first mount at front arrow 1, then at right rear arrow 2 and finally at left rear arrow 3.





- Disconnect the electrical harness connector from Knock Sensor (KS) 1 (G61) - 1 - or the electrical harness connector from Knock Sensor (KS) 2 (G66) - 2 -.

- Using a Multimeter, check Knock Sensor (KS) 1 (G61) or Knock Sensor (KS) 2 ( G66) component terminals 1+2 for a short to each other.

Specified value: infinite (No Continuity).

If the specification is not obtained:

- Replace the faulty Knock Sensor.

If the specification is obtained:

If the manufacturers test box is being used. Perform the following step.

- Install the Adapter Cable (121 Pin) (VAG1598/31 ).

- Using a Multimeter, check the following wiring connections for an open circuit.













Specified resistance 1.5 ohms max.

- Check the wiring for a short circuit to Battery positive (+) or an open circuit.

- If necessary, repair the wiring connection.

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

- Assembly is performed in the reverse of the removal.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code, Setting ] Readiness Code, Setting.

End of Diagnosis.