P1155

P1155

Oxygen Sensor Ahead of TWC, Bank 2 - Above Limit

Diagnosis conditions

NOTE: A lot of time is required (several days) until a fault is detected.

Possible fault cause
- Valve lift fault
- False air on the oxygen sensor after TWC
- Oxygen sensor

NOTE:
- As this fault can be caused by a faulty flat-base tappet, a system test for a small lift has to be performed initially. The fault can occur sporadically; the test should therefore be performed at least three times when the engine is at operating temperature.
- First indication of a valve lift fault can be provided by the adaptation values at idle speed (RKAT)and in the lower part load (FRAU) if they differ by more than 10%.

Perform system test for small lift

WARNING: Test is carried out while driving. Have a second person operate the Porsche System Tester 2.

During the system test for small lift, the valves remain at small lift, regardless of the type of driving. Faulty switching conditions can be detected by rough running, just like with misfire detection.

Several cylinders may be stored as faulty, although only one valve on one cylinder is faulty.

In order to ensure that the fault is repaired, the flat-base tappets of the inlet valves of the entire cylinder bank should be replaced if a fault occurs.

A faulty flat-base tappet can be detected because the oxygen sensor F(R) for this cylinder bank enriches the mixture (F(R) [>] 1) during acceleration with wide-open throttle - see drawing below. Difference from the other oxygen sensor [>] approx. 15 %. In the case of a fault, the flat-base tappets of the inlet valves for the entire cylinder bank must be replaced.







1 - Select system test.
2 - Select "Request small lift".
If "Valve lift diagnosis not ready" appears, a fault may have been stored.
1. Erase the fault memory.

3 - Activate the system test with the key [F8] immediately before acceleration with wide-open throttle.
The message "Drive link active" then appears.

NOTE: If "Request small lift" appears, the valves remain at small lift, i.e. the performance is reduced dramatically.

4 - Perform acceleration with wide-open throttle in 2nd gear, until "Valve lift diagnosis completed" (max. 4000 rpm) appears.
At speeds above 4000 rpm, misfires may be stored. Delete the fault memory and repeat the test.

NOTE:
- If a fault is detected, it is only recorded in the fault memory after 6,000 ignitions (at idling speed approx. 3 minutes waiting time).
- It is important to observe the oxygen sensors during acceleration with wide-open throttle or to record their behaviour with the data logger.

Diagnosis/Troubleshooting

NOTE:
- Do not use contact spray on the connectors to oxygen sensor.
- If other faults (fuel supply) are stored in the memory, rectify these first.







NOTE: Do not exchange oxygen sensors ahead of catalytic converter and after catalytic converter.







Oxygen sensors ahead of and after catalytic converter