Full Throttle Enrichment

1. Connect test harness VW 1315 A/1 between the differential pressure regulator and the harness plug.
2. Connect a multimeter to the test harness, set on the 20 mA scale.
3. Disconnect the harness plug from the coolant temperature sensor and bridge the terminals of the plug.
4. With the engine running above 4000 rpm, actuate the full throttle switch (on the throttle housing).
5. The differential pressure regulator current should increase to approx. 14 mA.
6. If the current reads too high, check the jumper wire at the temperature sensor connector.
7. If the current does not increase, check for a faulty full throttle switch, or a faulty RPM signal from the ignition control unit.