2. Select DME.
3. Call up the Drive links menu.
4. Select AIR pump.
5. Activate secondary air pump (audible function).
2 Check triggering of AIR pump.
1. Check fuse (Maxi Fuse) of AIR pump (on relay carrier 2).
2. Remove relay of AIR pump (on relay carrier 2). Connect voltmeter to pin 3 and ground.
Display: battery voltage
Connect voltmeter to pin 2 (negative) and pin 7 (positive).
Start engine (the DME relay must pick up).
Display: battery voltage
If 0 V is indicated, check wiring from pin 2 to DME control module, pin III/11, for continuity. Push relay back on.
3. Remove connector of AIR pump.
Connect voltmeter to pin 1 (positive) and pin 2 (negative).
Trigger AIR pump with Porsche System Tester 2.
Display: battery voltage
3 Check electric change-over valve.
1. Remove two-pole connector of electric change-over valve.
2. Connect voltmeter to pin 1 (positive) and pin 2 (negative).
3. Trigger AIR pump with Porsche System Tester 2.
Display: battery voltage
4. Remove vacuum hose of electric change-over valve with the engine running. Check whether vacuum is present.
4 Check air change-over valve and air supply lines.
1. Run engine briefly to produce vacuum.
2. Trigger AIR pump with Porsche System Tester 2.
3. Remove vacuum hose of air change-over valve.
If vacuum is present at the air change-over valve, check air supply from the AIR pump to the changeover valve up to the air supply line to the
cylinder heads.
Check function of air change-over valve.
DME 7.8
P1455
170 A/C compressor control - open circuit
Diagnosis conditions
- Engine running
- Battery voltage greater than 7 V
- Air conditioning on
Possible fault cause
- A/C relay
- Open circuit in wiring
Affected terminals
Terminal IV/27
Diagnosis/troubleshooting