Passat L4-1984cc 2.0L DOHC (9A) (1990)
Oxygen Sensor Harness Connector
5.
Disconnect the oxygen sensor harness connector.
Coolant Temperature Sensor
6.
Next, disconnect the harness connector from the coolant temperature sensor and connect a 2500 ohm resistance across the connector terminals to
simulate a cold engine. To check cold running enrichment, START the engine and let idle. Differential Pressure Regulator current should be
between:
15 and 25 mA for 6 to 9 seconds
7.
Then drop to between:
9 and 15 mA
8.
To test cold acceleration enrichment, open the throttle completely, then let it close. Differential Pressure Regulator current should increase briefly,
indicating cold acceleration enrichment.
9.
When the test is complete, turn the engine OFF. Reconnect the oxygen sensor and the coolant temperature sensor harness connector. Also
disconnect the ammeter from the Differential Pressure Regulator.
10.
These tests are only check the electrical portion of the Differential Pressure Regulator, to check the fuel pressure portion of the regulator refer to
FUEL SYSTEM PRESSURE TEST.