By Means of Short Test, Bank 1, Below Limit

P1127
418 Oxygen Sensing Error by means of Short Test, Bank 1 - Below Limit

P1134
419 Oxygen Sensing Error by means of Short Test, Bank 1 - Below Limit

Function
The adaptive oxygen sensing system corrects longer lasting deviations in the fuel/air mixture from 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.

Diagnosis conditions
- "Mixture adaptation" short test performed with the Porsche System Tester 2







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 signal from MAF sensor.

1. Connect special tool 9637.
2. Connect voltmeter to pin III/23 and ground.
Switch on the ignition.
Display: 0.9 to 1.1 V
Start engine.
Display: approx. 1.4 V

2 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 jumpering the fuel pump relay.
or
- via fuel pump relay without tester
Disconnect the fuel pump relay from the central electrical system and jumper plug-in contacts 30 and 87 (identification 3 and 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 (2.0 ± 0.5 ftlb.).

3 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 damage and deformation.

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

4 Check EVAP canister purge valve.

1. Disconnect hose from EVAP canister purge valve to intake system at EVAP canister purge valve.
2. Remove connector of EVAP canister purge valve.
3. Connect special tool 9160/1 to EVAP canister purge valve.
4. Generate vacuum of approx. 0.7 bar.
The vacuum must not fall below 0.5 bar after 10 minutes.