Checking Rear Window Defroster Signal

Auxiliary input signals, checking Rear window defroster signal

Requirement
- Engine Control Module (ECM) coding OK, Engine Control Module, refer to service and repair.

Checking
- Using VAG 1551 scan tool, select "Read Measuring Value Block" function 08, display group 004, display field 4, Display Group 000 - 008

Indicated on display, note value in display field 4:

Read measuring value block 4 -->
1 2 3 4

Specified value: OXX_XX

CAUTION: Do not use the shift inputs (identified by an X) during the RPM increase check.

- Switch ON rear window defroster.

Specified value: 1XX_XX

If display value is OK:
- Press button.
- Select "End Output" function 06.
- Press -Q- button to confirm input.

If display value does not change:
- Switch ignition OFF and connect VAG 1598/19 test box to ECM harness connector, Connecting VAG 1598/22 Test Box.
- Connect VAG 1 527B voltage tester between VAG 1598/19 test box socket C14 and Ground (GND).
- Switch ignition ON.
- Switch ON rear window defroster.
- Voltage tester must light up

If voltage tester does not light up:
- Check wiring for continuity between C14 and rear window defroster using wiring diagram.

If wiring is OK:
- Check rear window defroster using wiring diagram. If rear window defroster is OK:
- Replace ECM, Engine Control Module.