A8 Sedan V8-3.7L (AEW) (1997)
Rear Defogger: Testing and Inspection
Rear Window Defogger Signal, Checking
Rear Window Defogger Signal, Checking
NOTE: The Engine Control Module (ECM) receives a positive (+) voltage signal at terminal C22 when the rear window defogger is switched on.
Test conditions
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Vehicle at room temperature, greater than 15 °C (59 °F)
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Engine Coolant Temperature (ECT) at least 85 °C (185 °F)
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ECM coding OK
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Transmission selector lever in Neutral position
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Rear window defogger switched off
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Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at
idle). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1551 or VAG1552 Scan Tool" See: Powertrain
Management/Computers and Control Systems/Testing and Inspection
Indicated on display
Rapid data transfer
HELP
Select function XX
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Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block
Input display group number XXX
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Press buttons -0-, -2- and -4- to input display group number 24 (024), and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block 24
->
1
2
3
4
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Check specified values for rear window defogger operating condition (display field 4):
Specified value in display field 4: "R Def OFF"
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Switch rear window defogger on.
Specified value in display field 4: "R Def ON"
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Press -> button to advance program sequence.
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Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
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Stop engine (switch ignition off).
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Connect VAG1598/19 test box to ECM harness connector. Refer "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1598/19 Test
Box, Connecting" See: Powertrain Management/Computers and Control Systems/Testing and Inspection
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Connect VAG1527B LED voltage tester between ECM/test box sockets C22 and D11 (Ground).
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Switch ignition on.
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Switch rear window defogger on.