Knock Sensor 3, Checking

Observe all safety precautions: SAFETY PRECAUTIONS

View clean working conditions: CLEAN WORKING CONDITIONS

Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.

For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.

Special Tools And Workshop Equipment Required 

• multimeter.
• Wiring diagram.

Test requirements

• The mounting bolt of Knock Sensor 3 -G198- tightened to 20 Nm.
• The Motronic Engine Control Module (ECM) - J623- fuses OK.
  Fig 1: Fuses On E-Box In Engine Compartment, Left Side

  Courtesy of AUDI OF AMERICA, LLC
• 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. Refer to appropriate service information.

-- Disconnect the electrical harness connector Knock Sensor 3 -G198- -3-.

Checking internal resistance

-- Using a multimeter, check the Knock Sensor 3 -G198- terminals 1 to 2 for an internal short.

Specified value: ∞ (Infinity).

If the specified value was not obtained:

-- Replace the faulty Knock Sensor 3 -G198-. Refer to appropriate service 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 appropriate service information.

-- Using a multimeter, Check the Knock Sensor 3 -G198- electrical harness connector to the Motronic Engine Control Module (ECM) J623 electrical harness connector T105 for an open circuit.

Knock Sensor 3 -G198- electrical harness connector terminals	Motronic Engine Control Module (ECM) electrical harness connector T105 terminals
1	99
2	78
3	55

Specified value: 1.5 Ω Max.

If the specified value was not obtained:

-- Check the wiring connection for an open circuit.

-- 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 3 -G198-. Refer to appropriate service information.

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

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to appropriate service information.

-- Install the engine cover with air filter. Refer to appropriate service 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 .
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 .