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.