Idle Speed/Throttle Actuator - Electronic: Testing and Inspection

Electrical Check

Idle Air Control Valve Connection:

- Disconnect Idle Air Control (IAC) valve harness connector (arrow).
- Switch Digital Volt Ohm Multimeter (DVOM) to resistance range.

Idle Air Control Valve Testing:

- Connect multimeter across IAC valve terminals.
^ Must be 7-11 Ohms.

If NO:
- Replace IAC valve.

Mechanical Check

- Remove IAC valve from engine, leaving harness connector connected.

Idle Air Control Valve Inspection:

- Inspect rotary slide valve (arrow) for scoring.

CAUTION!:
When checking valve travel, DO NOT move rotary slide valve with screwdriver or other tool.

- Initiate Output Diagnostic Test Mode (DTM) until IAC valve is actuated. Refer to On-Board Diagnostics. Testing and Inspection
- Check whether rotary slide valve travels properly from stop to stop.

If scoring is severe enough to impair free movement.
- Replace IAC valve.

If the rotary slide valve:
^ Binds.
^ Runs slowly.
^ Will not travel to both stops.
- Replace IAC valve.

Checking Control Signal

- Disconnect harness connector for IAC valve.
- Connect US 1115 LED tester or equivalent (using adapter cable from connectortest kit VW 1594) between terminal 1 of harness connector and engine Ground (GND).
- Crank starter for a few seconds.
^ LED tester must light up.

If NO:
- Verify that injector valve circuit breaker -S72- and EVAP frequency valve circuit breaker -S75- in electronic control box are OK.
- Check continuity between terminal 1 of IAC valve harness connector and EVAP frequency valve circuit breaker -S75-, using wiring diagram.
^ Must be 0.5 ohm maximum.

Central Electric Panel With Detail Of Relay Position 6:

- Check continuity between EVAP frequency valve circuit breaker -S75- and terminal 31 of fuel pump relay -J17- (relay location 6).
- Check control signal to fuel pump relay.
- Reconnect LED tester.
- Activate Output DTM.
^ LED tester must light up.

Note: Positive voltage supply must always be present at terminal 1, regardless of which Output DTM is called up.

If LED tester does NOT light up:
- Connect VAG 1598 Test Box (using VAG 1598/5 adapter cable), to Engine Control Module (ECM) harness connector. Refer to VAG 1598 Pin Out Box Connecting Connecting and Testing VAG 1598 Pin Out Box
^ ECM remains disconnected.
- Check continuity (according to wiring diagram) between terminal 1 of IAC valve harness connector and terminal 37 of Test Box.
^ Must be 0.5 ohm maximum.

If NO continuity:
- Repair open circuit between terminal 37 of ECM harness connector and terminal 1 of IAC valve harness connector.

If NO open circuit:
- Replace ECM.
- Remove Test Box and VAG 1598/5 adapter cable.
- Reconnect ECM.
- Connect LED tester (using adapter cable) to terminals 1 and 2 of IAC valve harness connector.
- Activate Output DTM.
^ LED tester must blink when IAC valve is activated (blinking may be weak but must occur).

If LED tester does NOT blink, or if it lights up continuously:
- Connect VAG 1598 Test Box (using VAG 1598/5 adapter cable), to ECM harness connector.
^ ECM remains disconnected

If LED tester is continuously lit:
- Check for continuity between terminal 2 of IAC valve harness connector and terminal 4 of Test Box.

If LED tester does NOT blink:
- Check for continuity between terminal 2 of IAC valve harness connector and terminal 4 of Test Box.

If NO continuity:
- Repair short to GND or open circuit between terminal 2 of IAC valve harness connector and terminal 4 of ECM harness connector.

If NO open circuit or short to GND:
- Replace ECM.