Fault code 1800: Diagnosis/troubleshooting

NOTE:

Before replacing the control module, the ground connections, power supply and plug connections on the control module must be checked.
When replacing the vehicle electrical system control module, observe the coding of the control module.
After the test drive, read out the fault memory with the Porsche System Tester II No. 9588 again. Additional causes of faults that could damage the vehicle electrical system control module should be detected and remedied.

DIAGNOSIS/TROUBLESHOOTING CHART

Work instruction			Display OK	If not OK
1	Check lines for short circuit to B+:	Switch off the ignition. Pull out plug 'A' on vehicle electrical system control module: Pull out light switch plug. Switch on ignition. Measure voltage between vehicle electric system plug 'A' 'Pin 5, 17, 19' and ground.	< 0.3 V Go to Step 2	Repair / replace wiring harness → End
2	Check lines for short circuit to ground:	Switch off the ignition. Pull out plug 'A' on vehicle electrical system control module: Pull out light switch plug. Measure resistance between vehicle electric system plug 'A' 'Pin 5, 17, 19' and ground.	∞ Ω Go to Step 3	Repair / replace wiring harness → End
3	Check lines for open circuit:	Measure resistance between vehicle electric system plug 'A' 'Pin 5, 17, 19' and light switch plug 'Pin 2, 3, 1'.	< 5 Ω → > Step 4	Repair / replace wiring harness → End
4	Replace light switch on a trial basis: Erase fault memory. Satisfy diagnostic conditions Read out fault memory again		Fault code 1800 not entered. → End	Fault code 1800 re-entered. → > Step 5
5	Replace vehicle electrical system control module on a trial basis. Observe note		→ End