Function test

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Connect VAG 1551/1552Scan Tool.
See appropriate On Board Diagnostic (OBD) article.
Start engine and let idle.
Press buttons -0- and -1- to select "Engine electronics" address word 01.

Display will appear as shown

Fig 1: Indicating On Display Select Function XX

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Press buttons -0- and -8- to select "Read measuring value block" function 08.
Press -Q- button to enter input.

Display will appear as shown

Fig 2: Indicating On Display: Read Measuring Value Block

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Press buttons -0-, -7- and -1- to select "Display group 71".
Press -Q- button to enter input.

Display will appear as shown

Fig 3: Indicating On Display: Display Group 71

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Display will appear as shown

Check display in field 1:

Fig 4: Indicating On Display: Check END System OK
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DISPLAY GROUP 71: EVAPORATIVE EMISSIONS SYSTEM DIAGNOSIS (LEAK DIAGNOSIS)

	Display fields
	1	2	3	4
Display	Reed open Reed closed	Small leak/large leak Terminated	System Test Check Check end	Test OFF/Test ON System OK System not OK
Indicated	Reed contact condition	DTC message	System condition	Diagnostic conditions and diagnostic results
Working range	-	-	-	-
Spec.	Reed closed	-	END of Test	System OK

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 obtained:

Press 0 and 4 buttons to select Function 04 "Basic setting".
Press Q button to enter input

Display will appear as shown:

Fig 5: Indicating On Display: System In Basic Setting 71

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Evaporative emissions system test will begin. First, the function of the Reed switch (in Leak Detection Pump -V144-) is checked by the ECM.
After approx. 10 seconds the Leak Detection Pump -V144- will be activated and pressure will build up in the system.

Display will appear as shown:

Fig 6: Indicating On Display: Reed Open System Test On

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The test will be initiated after approx. 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.

Display will appear as shown

Fig 7: Indicating On Display: Reed Open Check Test On

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The Leak Detection Pump -V144- switches OFF and the ECM measures the time until the Reed contact closes.

Display will appear as shown

Fig 8: Indicating On Display: Reed Closed Check End System Ok

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Check display in fields 3 and 4:

DISPLAY GROUP 71: EVAPORATIVE EMISSIONS SYSTEM, DIAGNOSIS (LEAK DIAGNOSIS)

	Display fields
	1	2	3	4
Display	Reed closed	Small leak	Check	Test OFF/Test ON System OK
Display	Reed open	Large leak	System Test Check END	System not OK
Indicated	Reed contact condition	DTC display	Test status	Result
Working range	-	-	-	-
Spec.	Reed closed	-	END of Test	System OK
Spec.	-	If DTC appears: LEAK CHECKING .	If specifications not obtained: Check DTC memory.

If specifications obtained:

Press --> button.
Press 0 and 6 buttons to select Function 06: "End transfer"
Press Q button to enter input
Switch OFF ignition.

If specifications not obtained:

Press buttons -0- and -8- to select "Read measuring value block" function 08.
Press -Q- button to enter input.

Display will appear as shown

Fig 9: Indicating On Display: Read Measuring Value Block

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Press buttons -0-, -7- and -0- to select "Display group 70".
Press -Q- button to enter input.

Display will appear as shown (1 to 4 = Display fields)

Fig 10: Indicating On Display: Read Measuring Value Block 70

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Press buttons -0- and -4- to select "Basic setting" function 04.
- Tank vent valve diagnosis will be initiated

NOTE: Engine must not be under load during this time because diagnosis will be interrupted and will not restart until engine is accelerated.

Display will appear as shown (1 to 4 = Display fields)

Fig 11: Indicating On Display: System In Basic Setting 70

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When the diagnosis is initiated by the Engine Control Module, the display in display field 4 jumps from "Test OFF" to "Test ON".

Run engine at idle until specification "TEV OK" is shown in display field 4.

NOTE: If the display changes from "Test ON" to "Test OFF" during the test, briefly accelerate engine and the test will repeat.

DISPLAY GROUP 70: EVAPORATIVE EMISSIONS SYSTEM DIAGNOSTIC (TANK VENTING SYSTEM)

Display fields
1	2	3	4
Display	xxx %	xx.x %	xx.xx g/s	Test OFF / Test ON TEV OK TEV not OK
Indicated	Opening of solenoid valve during diagnosis	Oxygen sensor control deviation during diagnosis	Idle speed control deviation during diagnosis	Diagnostic conditions and diagnostic results
Working range	0 to 100 %	-25.0 to 25.0 %	-2.7 to 2.8 g/s	-
Spec.	-	-	-	TEV OK

If "TEV not OK" appears in display field 4:

Perform Output Diagnostic Test Mode and activate EVAP canister purge regulator valve -N80- using scan tool.

See appropriate On Board Diagnostic (OBD) article.

Display Readiness code using scan tool:

See appropriate On Board Diagnostic (OBD) article.

The Readiness code must be reset if the ECM is subject to low voltage with the ignition ON or if the DTC memory is erased.

See appropriate On Board Diagnostic (OBD) article.

If specification "TEV OK" obtained:

Press --> button.

Display will appear as shown

Fig 12: Indicating On Display: Select Function XX

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Press buttons -0- and -6- to select "End transfer" function 06.
Press -Q- button to enter input.
Switch ignition off.