Knock Sensor 1, Checking

Knock Sensor 1, 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) 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 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

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

- Disconnect the green Knock Sensor (KS) 1 (G61) electrical harness connector.

Checking internal resistance

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

Specified value: 4.84 M ohms (+/- 1 M ohms).

If the specified value was Not obtained:

- Replace the faulty Knock Sensor (KS) 1 (G61). Refer to the 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.

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

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to the Repair Information.

- 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. Refer to wiring diagrams.






Specified value: 1.5 ohms Max.

If the specified value was Not obtained:

- Check the wiring connection for an open circuit, high resistance or short circuit to Battery (+) or Ground.

- 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 sensor resistance was OK:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the Repair Information.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.