Leak Detection Pump, Checking

Special tools and workshop equipment required 

• Multimeter
• wiring diagram

Test requirements

• The Leak Detection Pump (LDP) -V144- fuse OK.
• The ignition switched off.

Test procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

Start diagnosis

-- Remove the right rear wheel housing liner. Refer to FRONT WHEEL HOUSING LINER .

-- Disconnect the electrical harness connector -3-.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

Checking internal resistance

-- Using a Multimeter --, check the pins at the Leak Detection Pump (LDP) -V144- for resistance as follows:

Leak Detection Pump (LDP) -V144- terminals	Specified value
-1- + -3-	640 to 720 Ω
-2- + -3-	15 to 17 Ω

If the specifications are not obtained:

-- Replace the Leak Detection Pump (LDP) --V144--.

If the specified values are obtained:

-- Check the voltage supply of the Leak Detection Pump (LDP) --V144--.

Checking voltage supply

-- Using the Multimeter --, check the electrical harness connector for voltage.

Leak Detection Pump (LDP) -V144- electrical harness connector terminal	Measure to
3	Engine Ground (GND)

-- Turn the key on.

Specified value: approx. battery voltage.

-- Switch the ignition off.

If the specified value was not obtained:

-- Using a Multimeter --, check electrical harness connector terminal -3- between Leak Detection Pump (LDP) -V144- and connector T-40 -- cavity 21 for open circuit.

Specified value: Wire resistance max 1.5 Ω.

If the specification is not obtained:

-- Check the wiring for a short circuit to Battery positive (+) or an open circuit.

-- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:

Checking output wiring

-- Install the Adapter Cable (121 Pin) VAG1598/31. Refer to Engine Mechanical, Fuel Injection & Ignition, Repair Group 24.

-- Using a Multimeter --, check the following wire connections for an open circuit.

Leak Detection Pump (LDP) -V144- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J623- electrical connector T121 terminal or test box socket
1	80
2	25

Specified value: Wire resistance max 1.5 Ω.

If the specification is not obtained:

-- Check the wiring for a short circuit to Battery positive (+) or an open circuit.

-- If necessary, repair the wiring connection.

-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY

-- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to READINESS CODE .

-- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to MOTRONIC ENGINE CONTROL MODULE, REPLACING .

Assembly is performed in the reverse order of the removal, note the following:

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE, SETTING .

End of diagnosis.