Leak Detection Pump, Checking

Leak detection pump, checking

Note: Beginning in 08.95, OBD II vehicles were produced with a Leak Detection Pump (LDP). The LDP was installed, but it was not activated.
As of 10.95 (V/N 1H_033489) the LDP was no longer installed.
Do not change the coding of the ECM in an attempt to activate the LDP.
The pump was reintroduced (and functional) for the 1997 model year

Special tools and equipment






Fluke 83 Multimeter
VAG 1527B Voltage tester
VW1594 Adapter Kit
Wiring Diagram

Leak Detection Pump voltage supply, checking

- Disconnect 3-pin harness connector to leak detection pump.

Test sequence






- Disconnect 3-pin harness connector from Leak Detection Pump -V144-.
- Connect VAG 1527 B Voltage Tester between connector terminal 3 (Battery Plus) and engine Ground.
- Start engine and let idle.
LED must light up.

If LED does not light up:

- Check wire between connector terminal 3 and relay panel for open circuit using wiring diagram.
Specification: max. 1.5 ohms

If LED lights up (voltage supply OK):






- Connect VAG 1598/18 test box to Engine Control Module (ECM) wiring harness.
- Check wiring for open circuit between test box and 3-pin leak detection pump connector as follows:
Terminal 1 and test box socket 46
Terminal 2 and test box socket 35
Specification: 1.5 ohms

- Check wires for short circuit to one another or ground using wiring diagram.

If no malfunction in voltage or wiring was found:

- Check Leak Detection Pump resistance.

Leak Detection Pump, resistance checking






- Disconnect 3-pin harness connector from Leak detection pump (LDP) -V144-.
- Switch Fluke 83 multimeter to resistance range.
- Connect Fluke 83 multimeter between terminals 1 and 3 of Leak Detection Pump -V144- and measure resistance.
Specification: 640 to 720 ohms

- Connect Fluke 83 multimeter between terminals 2 and 3 of Leak Detection Pump -V144- and measure resistance.
Specification: 12.5 to 19.5 ohms

If specifications not obtained:

- Replace Leak detection pump (LDP) -V144-.

If specifications OK:

- Replace Motronic Engine Control Module (ECM) -J220-.