Checking LDP Via Output DTM (W/Electronic Throttle Control)
Leak Detection Pump (LDP) -V144, checking
Special tools needed:
- VAG1526 A
- VAG1527 B
- VAG1594 A
- VAG1598/22 (vehicles with mechanical accelerator cable)
- VAG1598/31 (vehicles with electronic throttle control
- VAS5051 with VAS5051/1
or
- VAG1551 with VAG1551/3 A
Checking LDP via Output DTM (vehicles with electronic throttle control)
- Connect VAS5051 with diagnostic cable VAS5051/1 or VAG1551 Scan Tool (ST) with adapter cable VAG1551/3B.
NOTE: In the following description the performance of the On Board Diagnostic (OBD) procedure the VAG1551 Scan Tool (ST) is used. When using Vehicle Diagnostics Test and Information System VAS5051, use the operating instructions.
Indicated on display:
On Board Diagnostic HELP
1 - Rapid data transfer 1)
2 - Blink code 1)
1) Appears alternately
- Switch ignition on.
- Press button 1 to select "Rapid data transfer".
Indicated on display:
Rapid data transfer HELP
Enter address word XX
- Enter "01" for address word "Engine electronics" and confirm input by pressing Q button.
- Press -> button.
Indicated on display:
Rapid data transfer HELP
Select function XX
- Enter "03" for function "Output Diagnostic Test Mode (DTM)."
Indicated on display:
Rapid data transfer Q
03-Output Diagnostic Test Mode
- Confirm input by pressing Q-button.
Indicated on display (EVAP canister purge regulator valve -N80)
Output Diagnostic Test Mode ->
EVAP Purge Regulator Valve -N80
- Press -> button until following display is shown:
Indicated on display:
Output Diagnostic Test Mode ->
Leak Detection Pump
The leak detection pump is activated for about 1 minute.
NOTE: You can hear the leak detection pump run at the left rear wheel housing when it is working. This will be difficult to hear. Make sure to be as close to LDP as possible and to eliminate as much surrounding noise as possible.
If LDP -V144 is not activated (pump is silent):
- Switch ignition off.
- Remove LDP and disconnect electrical connector.
Checking resistance (all vehicles)
- Switch multimeter Fluke 83 to resistance and connect as follows:
Vehicles manufactured > approx. 05.97
Leak detection pump Specified value
terminal
1+3 640 to 720 Ohms
2+3 17.5 to 27.5 Ohms
Vehicles manufactured approx. 05.97 >
Leak detection pump Specified value
terminal
1+3 640 to 720 Ohms
2+3 15 to 17 Ohms
If you measure values other than specified values:
- Replace Leak Detection Pump (LDP) -V144.
If you reached specified values:
- Check voltage supply to electrical connector of LDP.
Checking voltage supply (all vehicles)
NOTE: Voltage supply to the LDP is via the fuel pump relay.
Test condition:
- Fuse for LDP is OK
- Disconnect connector from LDP.
- Connect voltage tester VAG1527 B as follows:
Connector terminal Measure
3 Engine Ground (GND)
- Briefly operate starter motor.
- LED must light up.
If LED does not light up:
- Check electrical wiring from terminal 3 via fuse for fuel pump relay for open circuit.
- Repair wiring as necessary.
If wiring is OK:
- Check fuel pump relay:
Checking output wiring (vehicles with electronic throttle control)
- Connect voltage tester VAG1527B as follows:
Electrical connector terminal Specification
2 Battery Positive
- Initiate Diagnostic Test Mode (DTM).
- Press -> button until following display is shown:
Indicated on display:
Output Diagnostic Test Mode ->
LDP leak test
- LED must blink
If LED does not blink:
- Switch ignition off.
- Remove weatherstrip at plenum chamber -arrows-.
- Remove cover for plenum chamber -1- toward front.
- Remove cover for E-box in plenum chamber.
- Carefully lever off clamp -arrow- with screwdriver.
NOTE: Disconnect or connect the Engine Control Module (ECM) connector only with ignition switched off.
- Unlatch clip and disconnect connector for Engine Control Module (ECM).
- Connect test box VAG1598/22 to harness connector. The ground clamp (not visible in the illustration) must be connected to battery ground connection. Do not connect ECM.
- Check the following wire connection for open circuit or short circuit to Ground or plus (B+):
Electrical connector terminal Test box VAG1598/22 socket
2 25
- Repair wiring or short circuit if necessary.
If you did not find any malfunction, however the Leak Detection Pump (LDP) did not function during the Output Diagnostic Test Mode (DTM):
- Replace LDP.
If the LED does not blink, although wiring is OK:
- Replace the Engine Control Module (ECM)
- Generate readiness code:
Checking input wiring (vehicles with electronic throttle control)
- Switch ignition off.
- Connect test box VAG1598/31 to harness connector, "Check output wiring."
- Check the following wire connections for open circuit or short circuit to Ground or plus (B+):
Electrical connector terminal Test box VAG1598/31 socket
1 80
- Repair open or short circuit as necessary.
- Generate readiness code: