Fault code 21: Diagnosis/troubleshooting

FAULT CODE 21 DIAGNOSIS PROCEDURE

Work instruction			Display OK	If not OK
1	Check temperature sensor	Switch off ignition Pull plug B off the air-conditioning system regulator Measure resistance on plug B between pin 5 and pin 9	approx. 1.2 k (at 23 °C) Step 2	Step 5
2	Check wiring between air-conditioning system regulator and temperature sensor for short to B+	Remove connector of temperature sensor Switch on ignition Measure voltage at plug B of the air-conditioning system regulator between pin 5 and ground Measure voltage at plug B of the air-conditioning system regulator between pin 9 and ground	0 V Step 3	Repair wiring harness -> End
3	Check wiring between air-conditioning system regulator and temperature sensor for short to ground	Measure resistance at plug B of the air-conditioning system regulator between pin 5 and ground	Step 4	Repair wiring harness -> End
4	Check wiring between air-conditioning system regulator and temperature sensor for interruption	Measure resistance between plug B on the air-conditioning system regulator pin 5 and plug on outside temperature sensor pin 1 Measure resistance between plug B on the air-conditioning system regulator pin 9 and plug on outside temperature sensor pin 2	< 5 Step 6	Repair wiring harness -> End
5	Replace temperature sensor		-> End
6	Replace air-conditioning system regulator		-> End