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
- Vehicle at room temperature, greater than 15 °C (59 °F)
- Engine Coolant Temperature (ECT) at least 85 °C (185 °F)
- ECM coding OK
- Transmission selector lever in Neutral position
- Rear window defogger switched off
- 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" Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- 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
- 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
- Check specified values for rear window defogger operating condition (display field 4):
Specified value in display field 4: "R Def OFF"
- Switch rear window defogger on.
Specified value in display field 4: "R Def ON"
- Press -> button to advance program sequence.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Stop engine (switch ignition off).
- Connect VAG1598/19 test box to ECM harness connector. Refer "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1598/19 Test Box, Connecting" Testing and Inspection
- Connect VAG1527B LED voltage tester between ECM/test box sockets C22 and D11 (Ground).
- Switch ignition on.
- Switch rear window defogger on.
LED must light up.
If LED does not light:
- Check for open circuit between ECM/test box socket C22 and rear window defogger switch.