With Manufacturer's Scan Tool
Evaporative Emissions (EVAP) system, checkingSpecial tools and equipment
^ VAG 1551/1552 Scan Tool
Note: The VAG1552 Scan Tool can be used instead of the VAG1551; however, a print-out is not possible.
^ VAG1551/3B adapter cable
Checking requirements
^ All fuses must be OK.
^ No malfunctions stored in DTC memory
Refer to Powertrain Management
^ All electrical consumers switched OFF, e.g. lights and rear window heater must be OFF
^ A/C switched OFF, if equipped.
^ Throttle valve angle less than 10% display group 03, display zone 3
^ Engine Coolant Temperature less than 95° Display group 04, display zone 3
^ Intake Air Temperature 90° maximum Display group 04, display zone 4
Test sequence
- Connect VAG1551 /1552 Scan Tool.
Refer to Powertrain Management
- Start engine and let idle.
- Press O and 1 buttons to select Address word 01 "Engine electronics". Press Q button to confirm input
Indicated on display
- Press O and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to confirm input
Indicated on display
- Press 0, 7 and 1 buttons to select "Display group 71"
- Press Q button to confirm input
Indicated on display
or
Indicated on display
- Check display in zone 1:
If "Reed open" appears in display group 1:
- Briefly open fuel tank cap to release pressure in fuel tank.
^ Reed switch will close
If specification is obtained:
- Press 0 and 4 buttons to select Function 04 "Basic setting".
- Press Q button to confirm input
- Press 0, 7 and 1 buttons to select "Display group 71 "
- Press Q button to confirm input
Indicated on display
^ Evaporative emissions system test will begin. First, the Function of the Reed switch (in Leak Detection Pump -V144-) will be checked by the ECM.
^ After approximately 10 seconds the Leak Detection Pump -V144- will be activated and pressure will build-up in the system.
Indicated on display
^ The test will be initiated after approximately 50 seconds, when sufficient pressure has built up in the fuel system; however, it could take as long as 120 seconds to build the pressure if the fuel level is low.
Indicated on display
^ The Leak Detection Pump -V144- switches OFF and the ECM measures the time until the Reed contact closes.
Indicated on display
- Check display in zones 3 and 4:
If the specification are obtained the display zone 3 shows "END of Test" and display zone 4 "System OK":
- Press (arrow) button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to confirm input
- Switch OFF ignition.
If specifications not obtained:
- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to confirm input
Indicated on display
- Press buttons 0, 7 and 0 to select "Display group 70"
- Press Q button to confirm input
Indicated on display (1 to 4 = Display zones)
- Press 0 and 4 buttons to select Function 04: "Basic setting"
^ Tank vent valve diagnosis will be initiated
Note: Engine must not be under load during this diagnosis because diagnosis will be interrupted and will not restart until engine is accelerated.
Indicated on display (1 to 4 = Display zones)
^ When the diagnosis is initiated by the Engine Control Module, the display in display zone 4 jumps from "Test OFF" to "Test ON"
- Run engine at idle until specification "TEV OK" is shown in display zone 4
Note: If display changes from "Test ON" to "Test OFF" during test, briefly accelerate engine and test will repeat.
If "TEV not OK" appears in display zone 4:
- Perform Output Diagnostic Test Mode and activate the EVAP canister purge regulator valve N80:
Refer to Powertrain Management
- Display Readiness code:
Refer to Powertrain Management
- Readiness code must be reset if ECM is subject to low voltage with ignition ON or if fault memory is erased.
Refer to Powertrain Management
If specification "TEV OK" is obtained:
- Press (arrow) button.
Indicated on display
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to confirm input
- Switch OFF ignition.
Leak checking
If a small or large leak is detected during the Evaporative Emissions (EVAP) system leak check, proceed as follows.
- Switch off ignition
- Check fuel tank cap is secure and seal is not damaged. Replace if necessary.
- Repeat functional check.
If malfunction is still present:
- Fold rear seat bench forward.
- Remove cover under seat bottom.
- Check if fuel supply unit nut is tight and if seal is not damaged. Replace if necessary.
- Tighten lock ring with special tool 3217.
- Repeat functional test.
If malfunction is still present:
- Remove right rear wheel housing liner.
- Check pressure hose between Leak Detection Pump (LDP) -V144- and EVAP canister. Replace if necessary.
- Check connecting lines and hoses between EVAP canister and EVAP canister purge regulator valve -N80, Refer to Powertrain Management, Service and Repair, Evaporative Emissions System, Overview
- Repeat functional test.
If malfunction is still present:
- Remove EVAP canister from wheel housing and check for cracks and leaks. Replace if necessary.
- Repeat functional check.