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 REAR WHEEL HOUSING LINER .

-- Disconnect the Leak Detection Pump (LDP) -V144- electrical harness connector -2-.

Checking internal resistance 

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

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

If any of the specifications are not obtained:

-- Replace the Leak Detection Pump (LDP) --V144--. Refer to Leak Detection Pump -V144- [ .

If the specified values are obtained:

Checking voltage supply 

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

-- Using a Multimeter --, check the Leak Detection Pump (LDP) --V144-- electrical harness connector terminal 3 for voltage.

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

-- Operate the starter briefly.

Specified value: battery voltage.

-- Switch the ignition off.

If the specified value was not obtained:

-- Using a Multimeter --, check the Leak Detection Pump (LDP) --V144-- electrical harness connector terminal 3 to the Engine Component Power Supply Relay -J757- terminal 2/87 for resistance.

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.

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

-- If necessary, repair the faulty wiring connection.

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

Checking wiring 

If the manufacturers test box is being used. Perform the following step.

-- Install the Test Box 105 Pin VAG1598/42.

If the manufacturers test box is not being used. Perform the following step.

-- Remove the Motronic Engine Control Module (ECM) -J623-. Refer to ENGINE CONTROL MODULE, REMOVING AND INSTALLING .

-- Using a Multimeter --, check the Leak Detection Pump (LDP) --V144-- electrical connector terminal 1 to Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminal 40 for resistance.

-- Using a Multimeter --, check the Leak Detection Pump (LDP) --V144-- electrical connector terminals to the Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminals for resistance.

Leak Detection Pump (LDP) --V144-- electrical harness connector terminals	Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminals or test box socket
-1-	40
-2-	8

Specified value: 1.5 Ω max.

If the specification is not obtained:

-- Check the wiring for an open circuit, short circuit to each other, Battery (+), and Ground (GND).

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

-- If necessary, repair the faulty wiring connection.

If no malfunction is found in wiring:

-- 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 ENGINE CONTROL MODULE, REMOVING AND INSTALLING .

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 .