P1127
P1127Oxygen Sensing Error by means of Short Test, Bank 1 - Below Limit
Diagnostic conditions
- Battery positive voltage between 10 V and 16 V
- Time elapsed after engine start-up greater than 10 seconds
- 'Fuel Supply' short test performed using the 9588 Porsche System Tester II
Possible fault cause
- Incorrect main charge signal
- Fuel pressure too low
- Fuel injector doesn't open completely
- DME control module faulty
Affected pins
-
Diagnosis/troubleshooting
NOTE: If connector A is disconnected from the DME control module and the ignition is or was switched on, the 'DME Control Module Timeout' fault is recorded in many control modules.
NOTE: If control module connector A was disconnected from the DME in the course of troubleshooting or if the voltage supply was interrupted elsewhere (battery, fuse), the throttle adjusting unit must be adapted.
NOTE: If this fault is set, both mass air flow sensors must essentially be checked since the main charge signal is calculated from both signals.
NOTE:
- If 'P0445 - Below Limit' is stored in memory, correct this fault first.
- An open EVAP canister purge valve can lead to the lean threshold being reached.
NOTE: The short tests 'Fuel Supply - Idle Speed' and 'Fuel Supply - Partial Load' are designed in such a way that faults in the fuel supply (oxygen sensing system) can be detected even without a road test. A fault entry following the short test means that a normal fault entry would have been recorded even after a longer road test The troubleshooting procedure is therefore identical to that specified in the reference chapters.
