Leak Detection Pump (LDP) -V144-, Checking

Leak Detection Pump (LDP) V144, Checking (Vehicles With MPI-engine)







Special tools, testers and auxiliary items required

Test conditions
- 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
- Test box V.A.G 1598/31
- Vehicle Diagnostic, Testing and Information System VAS 5051 A with diagnostic cable VAS 5051/5 A







Test conditions
- Ignition switched on.
- Vehicle Diagnostic, Testing and Information System VAS 5051 A connected, On-board diagnostics and vehicle system "01 Engine electronics" selected.







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







Display on VAS 5051 A:
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 Specified value
(LDP) Terminal
- 1 - + -3- 640 to 720 Ohms
- 2 - + -3- 15 to 17 Ohms

- Replace Leak Detection Pump (LDP) V144.

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







Checking voltage supply

NOTE: Voltage is supplied to the leak detection pump via the Fuel Pump (FP) relay J17.

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 Fuel Pump (FP) Relay J17 for open circuit according to wiring diagram.
- Repair open circuit in wiring according to wiring diagram.







Checking output wire
- 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:
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 the diagnostic function "06 - End output".
- Switch off ignition.







- Connect test box V.A.G 1598/31 to wiring harness connectors, with Engine Control Module (ECM) not connected. Connect Ground (GND) clip at test box to Ground (GND) (not visible in illustration).

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 Test box V.A.G 1598/31Socket
- 2 - 25

- 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 1598/31 to wiring harness connectors, with Engine Control Module (ECM) not connected. Connect Ground (GND) clip at test box to Ground (GND) (not visible in illustration).

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 Test box V.A.G 1598/31Socket
- 1 - 80

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