Idle/Throttle Speed Control Unit: Testing and Inspection

Idle air control (IAC) valve (N 71), checking

Requirement
VAG 1551 Scan Tool connected

Triggering, checking
- switch OFF ignition
- disconnect harness connector from IAC valve
- connect US 1115 LED tester to terminals 1 and 2 of harness connector
- switch ON ignition and perform Output DTM again until IAC valve (N 71) is triggered
- LED tester must flash

If NO
- perform Motronic system electrical checks


Resistance, checking
- remove ignition wire guide from cylinders 1, 3 and 5
- disconnect harness connector from IAC valve (N 71)
- switch Fluke 83 multimeter to resistance range
- connect multimeter between terminals 1 and 2 of IAC valve connector using jumper wires from VW 1594 adaptor kit
- must be between 10 and 20 Ohms