Knock Sensor, Checking

The following procedure is used to check Knock Sensor (KS) 1 G61 and 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 tightened to 20 Nm.
• The Engine Control Module (ECM) J623 fuses OK.
• Battery voltage at least 12.5 V.
• 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 .

• Disconnect the electrical harness connector - 1  - or - 2  - of the respective knock sensor.

1 - Knock Sensor (KS) 1 -G61-.

2 - Knock sensor (KS) 2 -G66-.

Checking internal resistance 

• Using a Multimeter , check as follows:
• Using a Multimeter , check the Knock Sensor (KS) 1 G61
• or Knock Sensor (KS) 2 G66 terminals 1 to 2, 2 to 3, and 1 to 3 for an internal short.

Knock Sensor Terminal
1 to 2
1 to 3
2 to 3

Specified value: ∞ (Infinity).

If the specified value was not obtained:

• Replace Knock Sensor (KS) 1 G61 or Knock Sensor (KS) 2 G66 as necessary. Refer to 24 - FUEL INJECTION SYSTEM .

If the specified value was obtained:

Checking wiring 

If the manufacturers test box is being used, perform the following step.

• Install the test box VAG1598/42. Refer to 24 - FUEL INJECTION SYSTEM .

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

• Remove the Engine Control Module (ECM) J623. Refer to → Engine Control Module, Replacing .
• Using a Multimeter , check the knock sensor electrical harness connector to the Engine Control Module (ECM) J623 electrical harness connector for resistance.

• Knock Sensor (KS) 1 -G61-

Knock Sensor Wiring Harness Connector Terminal	Engine Control Module (ECM) J623 Wiring Harness Connector Terminal or Test box Socket
1 Ground (GND)	41
2 (signal)	58
3 (shielding)	42

• Knock Sensor (KS) 2 -G66-

Knock Sensor Wiring Harness Connector Terminal	Engine Control Module (ECM) J623 Wiring Harness Connector Terminal or Test box Socket
1 Ground (GND)	56
2 (signal)	57
3 (shielding)	42

Specified value: 1.5 Ω max.

If the specified value was not obtained:

• Check the wiring for a short circuit to Battery positive (+) or an open circuit.
• If necessary, repair the wiring connection.

If no malfunction is found in the wiring and the resistance was not OK:

• Replace Knock Sensor (KS) 1 G61. Refer to 24 - FUEL INJECTION SYSTEM .
• Erase the DTC memory. Refer to → Diagnostic Mode 04 - Reset/Delete Diagnostic Data .
• Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to → Readiness Code .

• End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:

• Replace the Engine Control Module (ECM) J623. Refer to → 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.
2. If necessary, erase the DTC memory. Refer to Diagnostic Mode 04 - Reset/Delete Diagnostic Data .
3. If the DTC memory was erased, generate readiness code. Refer to Readiness Code .