Knock Sensors, Checking

The following procedure is used to diagnose all Knock Sensors --.

Special tools and workshop equipment 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. Refer to PRELIMINARY CHECK .

Start diagnosis 

-- Remove the engine cover with air filter.

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

Checking internal resistance 

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

Specified value: ∞ (Infinity).

If the specified value was not obtained:

-- Replace the faulty Knock Sensor (KS) 1 -G61- /Knock Sensor (KS) 2 -G66-.

If the specified value was obtained:

Checking wiring 

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

-- Install the Test Box 105 PinVAG1598/42.

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, REMOVING AND INSTALLING .

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

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

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

Specified value: 1.5 Ω 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 (KS) 1 -G61- /Knock Sensor (KS) 2 -G66-.

-- Erase the DTC memory. Refer to 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 .

-- End of 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-. Refer to ENGINE CONTROL MODULE, REMOVING AND INSTALLING .

-- 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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .