Leak Detection Pump (LDP) -V144, Checking
Special tools and equipment
- VAG1526 A
- VAG1527 B
- VAG1594 A
- VAG1598/31
- VAS5051 with VAS5051/1
or
- VAG1551 with VAG1551/3 A
Initiate output Diagnostic Test Mode (DTM) as follows.
- Connect VAS5051 with diagnostic cable VAS5051 or VAG1551 scan tool with diagnostic cable VAG1551/3A.
NOTE: The following description only explains implementation of On Board Diagnostic (OBD) using VAG1551 scan tool. When using VAS5051, observe the tester's instructions for use.
Indicated on display
VAG-ON BOARD DIAGNOSTIC HELP
1 - Rapid data transfer 1)
2 - Blink code output 1)
1) Operating modes 1 and 2 are displayed alternately
- Switch ignition on.
- Press button 1 to select "Rapid data transfer" operating mode 1.
Indicated on display
Rapid data transfer HELP
Insert address word XX
- Press buttons -0- and -1- to select "Engine electronics" and press -Q- button to confirm input.
- Press button.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press button -0- and -3- to select function "Output Diagnostic Test Mode".
Indicated on display
Rapid data transfer Q
03-Output Diagnostic Test Mode
- Confirm input with -Q- button.
Indicated on display (EVAP canister purge regulator valve -N80)
Output Diagnostic Test Mode ->
EVAP Can. Purge Regulator Valve -N80
- Press button until following display is indicated:
Indicated on display
Output Diagnostic Test Mode ->
Leak detection pump tank vent system
The Leak Detection Pump (LDP) -V144 will be activated for approx. 1 minute.
NOTE: Operating noise of Leak Detection Pump (LDP) is audible at left rear wheelhousing.
If Leak Detection Pump (LDP) is not activated (no audible operating sound)
- Switch ignition off.
- Remove Leak Detection Pump (LDP) -V144, and disconnect harness connector.
- Check the internal resistance of the LDP.
- Check the voltage supply for the LDP.
- Check the output wire of the LDP.
Checking internal resistance
- Connect multimeter for resistance measurement as follows.
LDP -V144 terminals Specified value
1+3 640-720 ohm
2+3 15-17 ohm
If specified values are not obtained:
- Replace Leak Detection Pump (LDP) -V144.
If specified values are obtained:
- Check voltage supply at harness connector of Leak Detection Pump (LDP).
Checking voltage supply
NOTE: Voltage supply for the Leak Detection Pump (LDP) runs via the Fuel Pump (FP) relay.
Test requirement
- Fuse for Leak Detection Pump (LDP) OK
- Disconnect harness connector at LDP.
- Connect VAG1527 B voltage tester as follows:
Electrical harness Measure to
connector terminal
3 Engine Ground (GND)
- Operate starter briefly.
LED must light.
If LED does not light:
- Check wire connection from terminal 3 via fuse to Fuel Pump (FP) relay for open circuit.
- Repair open circuit if necessary.
If wire connection is OK.
- Check Fuel Pump (FP) relay.
Checking output wire
- Connect VAG1527 B voltage tester as follows:
Electrical harness Measure to
connector terminal
2 B+
- Initiate output Diagnostic Test Mode (DTM).
- Press -> button until following display is indicated:
Indicated on display
Output Diagnostic Test Mode ->
Leak detection pump tank vent system
LED must light.
If LED does not light:
- Switch ignition off.
- Remove Phillips head screws -1- from the E-box cover.
- Unclip water box cover -2- from the bulkhead -arrows-.
- Remove water box cover.
- Pry fresh air intake grid up to remove Phillips head screws from rear of cover -right arrow-.
- Remove rest of screws.
- Remove E-box cover.
- Disengage locking lugs and disconnect harness connectors from Engine Control Module (ECM).
NOTE: The connector for the ECM can only be disconnected or connected with the ignition switched off
- Connect VAG1598/31 test box to multi-pin harness connectors. The Ground (GND) clip must be clipped to Ground (GND). The ECM must not be attached.
- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+.
Electrical harness VAG1598/31
connector terminal test box socket
2 25
- Repair open circuit or short circuit if necessary.
If no malfunction is identified, but the Leak Detection Pump (LDP) does not function during the output Diagnostic Test Mode (DTM).
- Replace Leak Detection Pump (LDP) -V144.
If LED does not blink, but wiring is OK
- Replace Engine Control Module (ECM).
After completing work:
- Generate readiness code.
If there is no DTC stored:
- Check input wire.
Checking input wire
- Switch ignition off.
- Connect VAG1598/31 test box to multi-pin harness connectors, refer to "Checking output wire".
- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+.
Electrical harness VAG1598/31 test
connector terminal box socket
1 80
- Repair open circuit to short circuit if necessary.
After completing work:
- Generate readiness code.