Knock Sensors, Checking

Knock Sensor, Checking

The following procedure is used to diagnose Knock Sensor (KS) 1 G61 / Knock Sensor (KS) 2 G66.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements
- The mounting bolt of Knock Sensor (KS) 1 G61 / Knock Sensor (KS) 2 G66 tightened to 20 Nm.
- The Motronic Engine Control Module (ECM) J623 fuses 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. Preliminary Check

Start diagnosis
- Remove the engine cover with air filter.







- Disconnect Knock Sensor (KS) 1 G61 electrical harness connector - 2 - or Knock Sensor (KS) 2 G66 electrical harness connector - 3 -.

Checking internal resistance







- Using a Multimeter, check the Knock Sensor terminals 1 to 2 for an internal short.

Knock Sensor terminals
1 to 2
1 to 3
2 to 3

Specified value: (Infinity).

If any of the specified values are not obtained:
- Replace the faulty Knock Sensor.

If the specified value was obtained:

Checking wiring
If the manufacturers test box is being used. Perform the following step.
- Install the test box.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J623.







- Using a Multimeter, Check the Knock Sensor electrical harness connector to the Motronic Engine Control Module (ECM) J623 electrical harness connector T60 for an open circuit.

Knock Sensor (KS) 1 G61 Motronic Engine Control Module (ECM)
electrical harness electrical harness connector T60
connector terminals terminals or test box sockets
1 39
2 54
3 52

Knock Sensor (KS) 2 G66 Motronic Engine Control Module (ECM)
electrical harness electrical harness connector T60
connector terminals terminals or test box sockets
1 9
2 24
3 52

Specified value: 1.5 Ohms Max.

If the specified value was not obtained:
- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).
- Check the wiring connection for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring and the resistance was not OK:
- Replace the faulty Knock Sensor.
- Erase the 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. Monitors, Trips, Drive Cycles and Readiness Codes
- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:
- Replace the Motronic Engine Control Module (ECM) J623.
- 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. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

End of diagnosis