Idle/Throttle Speed Control Unit: Testing and Inspection
Idle stabilization, checkingFunction, checking
- switch ON ignition
- idle stabilizer valve 1 must vibrate and hum
If NO
- switch Fluke 83 multimeter (US 1119 or equivalent) to resistance range
- disconnect harness connector from idle stabilizer valve
- connect multimeter across stabilizer valve terminals
- must be between 2 and 10 Ohms
If NO
- replace idle stabilizer valve
If YES
- reconnect stabilizer valve harness connector
- check stabilizer valve wiring for open circuit using wiring diagram
If wiring OK
- replace Digifant control unit (J 169)
Control, checking
Requirements
- engine oil temperature 80°C (176°F) minimum
- coolant temperature sensor (blue) OK
- idle speed 0K
- intake air system 0K (leak tight)
- switch multimeter to mA range
- connect test adaptor VAG 1315A/2 between idle stabilizer valve and its harness connector
- connect multimeter to terminals of VAG 1315A/2 adaptor using jumpers from VW 1594 adaptor kit
- start engine and let idle
- will run from 1 to 4 minutes at increased engine RPM
When idle speed is reduced approx. 100 RPM
- raise engine speed in excess of 3000 RPM 3 times then let idle
- control current must be 460 ± 60 mA and fluctuating
- disconnect blue coolant temperature sensor harness connector (arrow)
- control current must be 460 ± 60 and constant
If test conditions
NOTE: Idle speed stabilization control current is dependent upon engine load during idle. Due to the following loads the control current can vary between 400 and 1200 mA:
- engine cold
- A/C switched ON
- electrical consumers switched ON
- power steering at full lock