Differential Pressure Regulator: Testing and Inspection

Fig. 7 Differential Pressure Regulator Test Harness:

Fig. 14 Altitude/Current Graph:

The regulator is functionally identical to that of the CIS-E unit, only the closed loop current range is different. The operating range is +10mA to -10mA, and the normal operating point is 0mA. This is to ensure better engine operation if an electrical failure should cause the system to run in the default mode.
1. With the ignition OFF, connect test harness (VW 1315A/1 or equivalent, Fig. 7) between the differential pressure regulator and the wiring harness plug.
2. Connect a multi-meter to the test harness and set it on the 200mA range. (For altitude correction during normal running with oxygen sensor disconnected, see Fig. 14.)
3. Insert the spare fuse into the top of the fuel pump relay.
4. Turn the ignition ON, then remove the fuse after 4 seconds (DO NOT turn ignition OFF).
5. Fault code indicator light should display fault 4341
6. Current reading on meter should be 100 mA.
7. Close the full throttle switch, and current should drop to 10 mA.
8. Disconnect the harness plug and check voltage between terminal 2 and ground.
a. With the ignition ON, 4.5 - 5.0vdc should be available.
b. Check voltage between terminals 1 and 2. 4.5 - 5.0vdc should be available.
9. If current and voltage readings are within specification, replace the differential pressure regulator.
10. If the current and voltage readings are not within specification;
a. Check for continuity between terminal 1 of the differential pressure regulator harness plug, and terminal 4 of the injection control unit plug.
b. Check for continuity between terminal 2 of the differential pressure regulator harness plug, and terminal 5 of the injection control unit plug.
11. If resistance is more than 0.2 ohms, repair wiring as necessary.
12. If resistance is 0.2 ohms or less, replace the control unit.