12 Oxygen Sensor After TWC, Bank 1 - Above Limit

P0138

12 Oxygen Sensor After TWC, Bank 1 - Above Limit

Function
To diagnose the readiness for operation of the oxygen sensors, the position of the sensor voltage is evaluated (diagnosis is disabled in the case of certain faults or conditions).

Diagnosis conditions







The DME control module stores DTC P0138 when the sensor voltage is over 1.5 V for more than 5 seconds during active oxygen sensing after the TWC.

P0138:

NOTE: Diagnosis can be performed with the Porsche System Tester 2 in the Short test menu.

Wiring Diagram







Diagnosis Procedure

Part 1:

Part 2:

1 Check oxygen sensor.

NOTE: This check must be performed with the engine cold.

1. Remove oxygen sensor connector 1 after TWC.
2. Connect ohmmeter to pin 1 and pin 4 of the oxygen sensor connector towards the oxygen sensor.

Display: infinity ohms

3. Connect ohmmeter to pin 1 and pin 3 of the oxygen sensor connector towards the oxygen sensor.

Display: infinity ohms

If 0 - 5 ohms is displayed, replace oxygen sensor.

2 Check wiring harness.
1. Remove oxygen sensor connector 1 after TWC.
2. Connect special tool 9637 to wiring harness (DME control module connector).
DME control module is not connected.
3. Connect voltmeter to special tool 9637, pin II/17, and ground.
4. Switch on the ignition.

Display: 0 V

5. Switch off ignition.
6. Connect voltmeter to special tool 9637, pin II/11, and ground.
Switch on the ignition.

Display: 0 V

If battery voltage is displayed, check wiring harness for chafing and pinching damage.

3 Check output stage of DME control module.
1. Connect special tool 9637.
2. Remove oxygen sensor connector 1 after TWC.
3. Connect voltmeter to pins II/11 and II/17.
4. Switch on the ignition.

Display: approx. 450 mV

If display shows > 500 mV, replace DME control module.

4 Perform adaptation.
1. Switch on the ignition.
2. Wait one minute. Do not press the accelerator.
3. Switch off the ignition for at least 10 seconds.
4. Read out the fault memory