Knock Sensor (KS) 1 G61 / Knock Sensor (KS) 2 G66 / Knock Sensor 3 G198 / Knock Sensor 4 G199 , Checking

Knock Sensor (KS) 1 G61 / Knock Sensor (KS) 2 G66 / Knock Sensor 3 G198 / Knock Sensor 4 G199, 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.

NOTE: 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: Infinity (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.

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 Sensors' electrical harness connectors to the Motronic Engine Control Module (ECM) J623 electrical harness connector T121 for an open circuit.

Knock Sensor (KS) 1 G61 Motronic Engine Control
electrical harness connector Module (ECM) electrical
terminals harness connector T121 terminals
or test box sockets
1 99
2 106
3 93

Knock Sensor (KS) 2 G66 Motronic Engine Control
electrical harness connector Module (ECM) electrical
terminals harness connector T121 terminals
or test box sockets
1 99
2 107
3 93

Knock Sensor (KS) 3 G198 Motronic Engine Control
electrical harness connector Module (ECM) electrical
terminals harness connector T121 terminals
or test box sockets
1 99
2 31
3 93

Knock Sensor (KS) 4 G199 Motronic Engine Control
electrical harness connector Module (ECM) electrical
terminals harness connector T121 terminals or
test box sockets
1 99
2 16
3 93

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.

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.

Final procedures
After 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.

- End of diagnosis.