Operation CHARM: Car repair manuals for everyone.

20 Oxygen Sensor After TWC, Bank 2 - Signal Implausible



P0156

20 Oxygen Sensor After TWC, Bank 2 - Signal Implausible

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 P0156 when the sensor voltage is less than 60 mV for more than 60 seconds during active oxygen sensing after the TWC.


P0156:






NOTE:
- In the event of a fault in the mixture system and uncontrolled fresh air injection (secondary air injection system) or a leaking exhaust system in front of the sensor, the sensor voltage may lie around 0 V for a longer period, thereby wrongly indicating a fault.
- 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.
1. Heat the oxygen sensors (road test car under load or run engine without load at high rpm).
2. Connect Porsche System Tester 2 or scan tool and read voltage of oxygen sensor 2 after TWC.

Display: Voltage fluctuations between 0 mV and 800 mV.
- Oxygen sensor OK.

In the case of a display around 0 V, give several acceleration bursts for approx. 10 seconds at 6000 rpm. If 0 V is still displayed for 1 or 2 minutes, a short circuit has occurred between the signal wire and sensor ground.

3. Remove oxygen sensor connector 2 after TWC.
4. Connect voltmeter to pins 3 and 4 of oxygen sensor connector towards the DME control module.

Display: approx. 450 mV.
- Replace oxygen sensor.

Display: approx. 0 V
- Check wiring harness.

2 Check wiring harness.
1. Remove oxygen sensor connector.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. With an ohmmeter, measure resistance between special tool 9637, pin II/14, and oxygen sensor connector, pin 4.

Display: 0 - 5 ohms

4. With an ohmmeter, measure resistance between special tool 9637, pin II/8, and oxygen sensor connector, pin 3.

Display: 0 - 5 ohms

3 Check output stage of DME control module.
1. Connect special tool 9637.
2. Remove oxygen sensor connector 2 after TWC.
3. Connect voltmeter to pins II/8 and II/14.
4. Switch on the ignition.

Display: approx. 450 mV

If display shows less then 400 mV or greater then 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.