Leak Detection Pump (LDP) V144 , Checking

Leak Detection Pump (LDP) V144, Checking (vehicles with FSI and TFSI-engine)







Special tools, testers and auxiliary items required
- Hand multimeter V.A.G 1526 A or V.A.G 1526 B
- Voltage tester V.A.G 1527 B
- Connector test kit V.A.G 1594 A or V.A.G 1594 C
- Adapter cable V.A.G 1598/39
- Test box V.A.G 1598/42
- Vehicle Diagnostic, Testing and Information System VAS 5051 with diagnostic cable VAS 5051/5 A

Test conditions
- Ignition switched on.







- Vehicle Diagnostic, Testing and Information System VAS 5051 with diagnostic cable VAS 5051/5 A connected, On-board diagnostics and Data Link Connector DLC "01 Engine electronics" selected.

Check activation







Display on VAS 5051 :
- In selection - 1 - , click on diagnostic function "03 - Output Diagnostic Test Mode (DTM)" .







Display on VAS 5051:
A - Output diagnostic test mode waiting, advancing by switching required
1 - Evaporative Emission (EVAP) Canister Purge Regulator Valve N80
- Press -> button repeatedly until leak detection pump for fuel system is activated

NOTE: Operating noise of Leak Detection Pump (LDP) is audible at left rear wheelhousing.

- End function "03 - output Diagnostic Test Mode (DTM)" by pressing <- button.
- From selection, click on diagnostic function "06 - End output" .
- Switch off ignition.

If Leak Detection Pump (LDP) for fuel system is not activated (no operating noise audible):
- Remove leak detection pump (LDP) V144 and disconnect the electrical connection.







Checking internal resistance
- Connect hand multimeter V.A.G 1526 A or V.A.G 1526 B for resistance measurement as follows.

Leak detection pump (LDP) Terminal Specified value
- 1 - + - 3 - 640 to 720 Ohms
- 2 - + - 3 - 15 to 17 Ohms

If specifications are not obtained:
- Replace Leak Detection Pump (LDP) V144.

If specified values are achieved:
- Check voltage supply of leak detection pump .







Checking voltage supply

NOTE: Voltage for leak detection pump is supplied via Motronic Engine Control Module (ECM) Power Supply Relay J271 .

Test conditions
- Fuse for leak detection pump OK

- Connect voltage tester V.A.G 1527 B as follows:

Harness connector Terminal Measure to
- 3 - Engine Ground (GND)

- Briefly operate starter.
- LED must light up.

If LED does not light up:
- Check electrical harness connection from terminal - 3 - via fuse to Motronic Engine Control Module (ECM) Power Supply Relay J271 for open circuit according to wiring diagram.







- Repair open circuit in wiring according to wiring diagram.







Checking output wiring
- Connect voltage tester V.A.G 1527 B as follows:

Harness connector Terminal Measure to
- 2 - Battery positive (B+)

- Initiate output Diagnostic Test Mode (DTM) .







Display on VAS 5051 :
A - Output diagnostic test mode waiting, Advancing by switching required
1 - Evaporative Emission (EVAP) Canister Purge Regulator Valve N80

- Press -> button repeatedly until leak detection pump for fuel system is activated

- LED must blink.

If LED does not blink:
- End function "03 - output Diagnostic Test Mode (DTM)" by pressing <- button.
- From selection, click on diagnostic function "06 - End output".
- Switch off ignition.







- Connect test box V.A.G 1598/42 to wiring harness with adapter cable V.A.G 1598/39-1 or adapter cable V.A.G 1598/39-2 . Clamp test box Ground (GND) clip to battery negative terminal. The procedure will indicate whether the engine control module is to be connected to the test box or not.

CAUTION: To avoid damaging electronic components, switch to the corresponding measuring range and observe all test conditions before connecting the test leads.







- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:

Harness connector Terminal V.A.G 1598/42 Bushing
- 2 - 4-Cyl. TFSI: B 8
6-Cyl. FSI: B 24
8-cyl. FSI - Audi RS4: A 55

- Repair wiring open circuit or short circuit according to wiring diagram.

If no malfunction is found, but leak diagnosis pump is not functional during output diagnostic test mode:
- Replace Leak Detection Pump (LDP) V144.
- Observe procedures for after re-connecting engine control module (ECM).

Checking input wiring
- Switch off ignition.







- Connect test box V.A.G 1598/42 to wiring harness with adapter cable V.A.G 1598/39-1 or adapter cable V.A.G 1598/39-2 . Clamp test box Ground (GND) clip to battery negative terminal. The procedure will indicate whether the engine control module is to be connected to the test box or not.

CAUTION: To avoid damaging electronic components, switch to the corresponding measuring range and observe all test conditions before connecting the test leads.







- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:

Harness connector Terminal V.A.G 1598/42 Bushing
- 1 - 4-cyl. TFSI: B 48
6-cyl. FSI: B 24
8-cyl. FSI - Audi RS4: B 40

- Repair wiring open circuit or short circuit according to wiring diagram.
- Observe procedures for after re-connecting engine control module (ECM).