Knock Sensor: Testing and Inspection

Knock Sensors, Checking

The following procedure is used to diagnose all Knock Sensors.

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)/Knock Sensor 3 (G198)/Knock Sensor 4 (G199 ) 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.

Procedure

- Remove the engine cover with air filter Refer to Fuel Injection and Ignition Repair Information.

• Before disconnecting the Knock Sensor electrical harness connectors, mark the component location.

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

- or Knock Sensor 3 (G198)

- or Knock Sensor 4 (G199)





Checking internal resistance

- Using a Multimeter, check each Knock Sensors' terminals 1 to 2 for an internal short.





Specified value: infinite (Infinity).

If the specified value was not obtained:

- Replace the faulty Knock Sensor (KS) 1 (G61)/or Knock Sensor (KS) 2 (G66) /or Knock Sensor 3 (G198)/or Knock Sensor 4 (G199)Refer to Fuel Injection and Ignition Repair Information.

If the specified value was obtained:

Checking wiring

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

- Install the test box. Refer to Fuel Injection and Ignition Repair Information.

If the manufacturers test box is not being used. Perform the following step.

- Remove the Motronic Engine Control Module (ECM) ( J623). Refer to => [ Engine Control Module, Replacing ] Service and Repair

- Using a Multimeter, Check the Knock Sensors' electrical harness connectors to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T121 for an open circuit.





















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, lose 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 (KS) 1 (G61)/Knock Sensor (KS) 2 (G66)/ or Knock Sensor 3 (G198)/ or Knock Sensor 4 (G199)Refer to Fuel Injection and Ignition Repair Information.

If no malfunction is found in the wiring and the resistance was OK:

- Replace the Motronic Engine Control Module (ECM) (J623).

- Install the engine cover with air filter Refer to Fuel Injection and Ignition Repair Information.

Final procedures

After 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 ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End of diagnosis.