Leak Detection Pump (LDP) -V144-, Checking
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
Observe Safety measures.
Observe Rules of cleanliness.
Checking LDP via Read Measuring Value Block (vehicles with mechanical throttle control)
NOTE: Always replace O-rings, sealing rings and gaskets.
Radiator fan must not come on during the test!
Troubleshooting requirements
- DTC memory checked and no DTCs stored
- All electrical consumers switched OFF
- A/C switched OFF
- Intake Air Temperature lower than 90°C See Display group 004, channel 4.
- Engine Coolant Temperature less than 95°C Display group 004, channel 3.
- Throttle angle less than 10°% Display group 003, channel 3.
- Connect VAS5051 with diagnostic cable VAS5051/1 or VAG1551 Scan Tool (ST) with adapter cable VAG1551/3B.
- Start engine and let idle.
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.
On Board Diagnostic HELP
1 - Rapid data transfer 1)
2 - Blink code 1)
Indicated on display:
1) Appears alternately
- Switch ignition on.
- Press button 1 to select "Rapid data transfer".
Rapid data transfer HELP
Enter address word XX
Display will appear as shown
- Press 0 and 1 buttons to select Address word 01: "Engine electronics".
- Press Q button to enter input.
- Press -> button.
Rapid data transfer HELP
Select Function XX
Display will appear as shown
- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input.
Read measuring value block
Enter display group number XXX
Display will appear as shown
- Press 0, 7 and 1 buttons to select "display group 71".
- Press Q button to enter input.
Read measuring value block ->
Reed closed break Test OFF
Display will appear as shown
NOTE: Condition for continuing test is "Reed closed" on the display.
The display does not always show "Abort".
If the display. "reed open" appears: Briefly open the filler cap to reduce pressure - this will close the reed contact. Continue checking as follows:
- Press 0 and 4 buttons to select Function 04: "Basic Setting".
System in basic adjustment 71 ->
Reed closed Test ON
Display will appear as shown
- The EVAP canister valve is opened to allow pressure relief in the system.
- Then the LDP -V144 will be triggered.
- The total procedure lasts approx. 60 seconds.
- Press -> button
System in Basic Adjustment 71 ->
Reed open Syst.Test Test ON
Display will appear as shown
- Measurement phase begins. The LDP -V144 is switched off and the ECM checks whether the reed contact has closed within 10 seconds.
If NO
System in Basic Adjustment 71 ->
Reed open Messg.END Syst. OK
Display will appear as shown
- The system is sealed and the measurement is ended.
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End output"
- Press Q button to enter input.
If contact does not close within 10 seconds.
- The LDP -V144 performs 4 pump strokes. The ECM compares the time it takes to carry out the pump strokes and the time until the reed contact closes again.
System in Basic Adjustment 71 ->
Reed clos fine leak Messg. ENDSyst.n OK
Display will appear as shown
- The system has recognized a fine leak (dia. greater than 1 mm).
System in Basic Adjustment 71 ->
Reed clos Irg leak Messg. ENDSyst.not OK
Display will appear as shown
- The Leak detection system has recognized a large leak.
- Press -> button.
If system has recognized a fine or large leak
- Check tank system and tank ventilation system for leaks.
- Perform tank leak diagnosis again.
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.
On Board Diagnostic HELP
1 - Rapid data transfer 1)
2 - Blink code 1)
Indicated on display:
1) Appears alternately
- Switch ignition on.
- Press button 1 to select "Rapid data transfer".
Rapid data transfer HELP
Enter address word XX
Indicated on display:
- Enter "01" for address word "Engine electronics" and confirm input by pressing Q button.
- Press -> button.
Rapid data transfer HELP
Select function XX
Indicated on display:
- Enter "03" for function "Output Diagnostic Test Mode (DTM)."
Rapid data transfer Q
03-Output Diagnostic Test Mode
Indicated on display:
- Confirm input by pressing Q-button.
Output Diagnostic Test Mode ->
EVAP Purge Regulator Valve -N80
Indicated on display (EVAP canister purge regulator valve -N80)
- Press -> button until following display is shown:
Output Diagnostic Test Mode ->
Leak Detection Pump
Indicated on display:
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:
Output Diagnostic Test Mode ->
LDP leak test
Indicated on display:
- 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: