LDP Via Read Measuring Value Block (Mechanical Throttle)
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 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.
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".
Display will appear as shown
Rapid data transfer HELP
Enter address word XX
- Press 0 and 1 buttons to select Address word 01: "Engine electronics".
- Press Q button to enter input.
- Press -> button.
Display will appear as shown
Rapid data transfer HELP
Select Function XX
- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input.
Display will appear as shown
Read measuring value block
Enter display group number XXX
- Press 0, 7 and 1 buttons to select "display group 71".
- Press Q button to enter input.
Display will appear as shown
Read measuring value block ->
Reed closed break Test OFF
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".
Display will appear as shown
System in basic adjustment 71 ->
Reed closed Test ON
- 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
Display will appear as shown
System in Basic Adjustment 71 ->
Reed open Syst.Test Test ON
- The system makes a test, the LDP -V144 starts running and shuts off when the pump running time reaches a pre-determined time-out.
- The total procedure lasts approx. 60 seconds.
Display will appear as shown
System in Basic Adjustment 71 ->
Reed open Measurement Test >ON
- Measurement phase begins. The LDP -V144 is switched off and the ECM checks whether the reed contact has closed within 10 seconds.
If NO
Display will appear as shown
System in Basic Adjustment 71 ->
Reed open Messg.END Syst. OK
- 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.
Display will appear as shown
System in Basic Adjustment 71 ->
Reed clos fine leak Messg. ENDSyst.n OK
- The system has recognized a fine leak (dia. greater than 1 mm).
Display will appear as shown
System in Basic Adjustment 71 ->
Reed clos Irg leak Messg. ENDSyst.not OK
- 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. Testing and Inspection
- Perform tank leak diagnosis again.
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 mechanical throttle activator)
- 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. Do not connect ECM.
- Check the following wire connection for open circuit and short circuit to Ground (GND) or to plus (B+):
Electrical connector terminal Test box VAG1598/22 socket
2 16
- Repair wiring or short circuit as 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 Leak Detection Pump (LDP) -V144.
If the LED does not blink, although wiring is OK:
- Replace Engine Control Module (ECM):
- Generate readiness code:
Checking input wiring (vehicles with mechanical throttle activator)
- Switch ignition off.
- Connect test box VAG1598/22 to harness connector, "Checking output wiring."
- Check the following wire connections for open circuit or short circuit to Ground or plus (B+):
Electrical connector terminal Test box VAG1598/22 socket
2 37
- Repair open or short circuit as necessary.
- Generate readiness code: