EGR Functional Check

Make sure all vacuum lines are in good condition, and that all hose connections are tight.
1. Switch the ignition OFF.
2. Disconnect the temperature sensor harness plug.
3. Switch multimeter to 2 megohm scale.
4. Using a test harness that allows the temperature sensor to remain connected (VAG 1594 or equivalent), connect the multimeter to terminals 1 and 2 of the test harness with wires long enough to allow the multimeter to be placed on the passenger seat.
5. Start the engine and let it idle until it reaches operating temperature (radiator fan should cycle on and off at least once).
6. Switch OFF the ignition and wait ten minutes. Resistance should be at least 20,000 Ohms.
If resistance is not within specification, replace the EGR temperature sensor.
7. Start the engine and let it idle for about three minutes.
8. Switch multimeter to 200k Ohm range.
9. Drive vehicle at a constant 50 - 60 MPH on a flat road for about two and a half miles.
NOTE, A/C should be OFF, and driving should be done in top gear.
10. During the test drive, watch the On Board Diagnostic (OBD) warning light. When the light flashes, resistance should be at least 50,000 Ohms.
11. If the resistance is less than 50,000 Ohms check the EGR system vacuum hoses and connections.