With Manufacturer's Scan Tool

Leak Detection Pump (LDP) -V144-, Checking

Special tools and equipment

- VAG1526 A
- VAG1527 B
- VAG1594 A
- VAG1598/22 (Vehicles with mechanical accelerator linkage)
- VAG1598/31 (Vehicles with Electronic throttle [drive by wire)
- VAS5051 with VAS5051/1
or
- VAG1551 with VAG1551/3 A

Test sequence:
- Ignition switched on

- Vehicle diagnosis - measuring and information system VAS 5051 attached, vehicle self-diagnosis and vehicle system "01 - engine electronics" selected.

Test procedure
VAS 5051 selection screen:

- Select the diagnostic function -1- "03 - control module diagnosis".
- Touch key until the leakage diagnostic pump/tank ventilation system is started.

- The diagnostic pump for fuel system is running for approximately 1 minute.

NOTE: The noise of the diagnostic pump (running) is audible at the rear left wheel housing.

- Quit function "03 - control module diagnosis" by touching <- key
- Select "06 - End output"
- Switch ignition off

If diagnostic pump is not activated (no operating noise audible):
- Remove Leak Detection Pump (LDP) -V144- and disconnect connector.

Internal resistance test

- Connect circuit analyzer as follows to perform resistance test.

Leak detection pump (LDP) -V144 Connector Desired value
1 + 3 640 ... 720 Ohm
2 + 3 15 ... 17 Ohm

Desired values are not reached:
- Replace Leak Detection Pump (LDP) -V144-.

Desired values are reached:
- Test voltage supply for Leak Detection Pump (LDP) -V144-.

Voltage supply test

NOTE: Voltage supply for the diagnostic pump is made by the fuel pump relay.

Test condition:
- Safety device for diagnostic pump i.O.

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

Connector terminal Measure against
3 Engine ground

- Briefly operate the starter
- Light Emitting Diode (LED) must flash

If light emitting diode does not shine:

- Check the electrical harness for an open from terminal 3 over the fuse to the fuel pump relay according to the electrical schematics.
- If necessary, repair wiring problem using circuit diagram.

Output circuit checking - Vehicles with mechanical accelerator operation

- Connect VAG 1527 B as follows:

Connector Terminal Measure against
2 Battery Pos. (+)

- Begin output check diagnosis and activate the diagnosis pump.
- Light Emitting Diode (LED) must flash

If Light Emitting Diode (LED) does not flash:
- Quit function "03 - control module diagnosis" by touching <- key.
- Select "06 - End output"
- Switch ignition off.

- Connect test box VAG1598/31 to the circuit harness connector; do not connect the ECM.

WARNING: To avoid damaging electrical components, select the appropriate measurement settings on the measuring device before connecting to the components.

- Check the following circuit connections for open circuits and shorts to ground and/or battery positive (+):

Connector terminal Test box V.A.G 1598/22 Socket
2 16

- Repair short circuit and/or circuit malfunction using circuit diagram

If no problem is found, but the diagnosis pump still does not work during the Output check diagnosis:
- Replace Leak Detection Pump (LDP).
- Observe the measures after reconnecting the ECM

Input circuit checking - Vehicles with mechanical accelerator operation

- Input circuit checking - Vehicles with mechanical accelerator operation.

WARNING: To avoid damaging electrical components, select the appropriate measurement settings on the measuring device before connecting to the components.

- Check the following circuit connections for open circuits and shorts to ground and/or battery positive (+):

Connector terminal Test box V.A.G 1598/22 Socket
1 37

- Repair short circuit and/or circuit malfunction using circuit diagram
- Observe the measures after reconnecting ECM

Output circuit checking - Vehicles with electronic engine power control (drive-by wire)

- Connect VAG 1527 B as follows:

Connector terminal Measure against
2 Battery Pos. (+)

- Begin output check diagnosis and activate the diagnosis pump.
- Light Emitting Diode (LED) must flash

If Light Emitting Diode (LED) does not flash:
- Quit function "03 - control module diagnosis" by touching <-
- Select "06 - End output"
- Switch ignition off

- Connect test box VAG1598/31 to the circuit harness connector; do not connect the ECM. Connect the ground clip of the test box to ground (not shown in illustration).

WARNING: To avoid damaging electrical components, select the appropriate measurement settings on the measuring device before connecting to the components.

- Check the following circuit connections for open circuits and shorts to ground and/or battery positive:

Connector terminal Test box VAG 1598/31 Socket
2 25

- Repair circuit malfunction using circuit diagram

If no problem is found, but the diagnosis pump still does not work during the Output check diagnosis:
- Replace Leak detection pump (LDP) -V144-.
- Observe the measures after reconnecting ECM.

Input circuit checking - Vehicles with electronic engine power control (drive-by wire)

- Check the following circuit connections for open circuits and shorts to ground and/or battery positive:

Connector terminal Test box VAG 1598/31 Socket
1 80

- Repair circuit malfunction using circuit diagram
- Observe the measures after reconnecting ECM