Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Lean Threshold

P1125

Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Lean Threshold

Function
The adaptive oxygen sensing system corrects longer lasting deviations in the fuel/air mixture of lambda = 1 by changing the anticipatory control calculated in the DME control module and the injection timing altered as a result. Should the correction factor through adaptation exceed a predetermined value, the diagnosis will detect the adaptation threshold.
Area 1 covers the engine operating state close to idle.

Diagnosis conditions
- Oxygen sensing system active.
- Time elapsed after engine start-up 250 to 350 sec.
- Engine temperature [>] 62 °C.
- Intake air temperature [<] 90 °C.
- Air mass flow [<] 29 kg/h.
- Engine speed [<] 800 rpm.

P1127-P1129:

NOTE: If DTC P0445 (EVAP canister purge valve - short to ground) is stored in the memory, correct this fault first. An open EVAP canister purge valve can lead to the lean threshold being reached.

Diagnosis Procedure







1 Check fuel pressure.








1. Undo and remove the closure cap of the fuel collection pipe test connection (A/F 13 mm).
2. Connect pressure gauge (special tool P 378a) to connecting line (special tool 9559) and connect to test connection.
3. Actuate fuel pump, either
- with Porsche System Tester 2
The fuel pump can be actuated with the Porsche System Tester 2 or by bridging the fuel pump relay.

or

- via fuel pump relay without tester
Disconnect the fuel pump relay from the central electrical system and bridge plug-in contacts 30 and 87 (identification 3 fund 5 on central electrical system) with a fused shop-made cable. The fuel pump must now operate or deliver fuel.

4. Nominal test values
Stationary engine 3.8 ± 0.2 bar
Engine idling 3.3 ± 0.2 bar

NOTE: The seal or sealing ring in the brass closure cap is not exchangeable. It must therefore be used only once.

Tightening torque of new brass closure cap 2.5 ± 0.5 Nm.


2 Check fuel pressure regulator, vacuum connection and fuel return line.

1. Remove vacuum hose from fuel pressure regulator.
2. Connect special tool 9103/2 to vacuum hose.
3. Start the engine.
Display: 0.4 - 0.6 bar

If the value is not attained, check the intake air system for leaks and check vacuum line to fuel pressure regulator for restrictions.

4. Check housing of fuel pressure regulator for outside damage.

Replace the fuel pressure regulator if it is damaged with the result that the spring pre-tensioning is increased.