With Manufacturer's Scan Tool
Signal From/To Air Conditioning System, Checking
Special tools and equipment
- V.A.G 1551 scan tool or 1552 scan tool with cable VAG 1551/3
- Test box VAG 1598/31
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram
Test conditions
- Air conditioner functioning OK.
- Air conditioner must be switched off
- No faults must be stored in DTC memory Reading Diagnostic Trouble Codes
- Vehicle at room temperature (warmer than +15°C).
Test sequence
- Connect V.A.G 1551 scan tool ((VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idling speed. [1][2]Reading and Clearing Diagnostic Trouble Codes
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for the function "Read measuring value block" and confirm entry with Q key.
Indicated on display:
Read measuring value block
Input display group number XXX
- Press keys 0, 5 and 0 for "Display group number 50" and confirm entry with Q key.
Indicated on display: (1 to 4 = Display zones)
Read measuring value block 50 ->
1 2 3 4
- Observe display in display zone 4. It must show
Compr. OFF.
- Switch on air conditioning system.
- Select lowest temperature and highest blower speed.
The display in display zone 4 must change to
Compr. ON.
- Floor accelerator pedal quickly and then release (brief burst of throttle).
The display in display zone 4 must change from
Compr.ON
to
Compr. OFF
for a few seconds (compressor switch-off when vehicle is accelerating).
- Press the -> key.
- Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
- Switch off ignition.
If the display does not change:
- Remove wiper arms and cowl panel
- Connect test box VAG 1598/31 to control module wiring harness. The engine control module remains disconnected.
- Check wiring for open circuit between test box sockets 40 + 41 and air conditioner system using wiring diagram.
Wire resistance: max. 1.5 Ohms
If no fault can be found in the wiring:
- Check function of air conditioner control module.
- Check DTC memory, if necessary, repair any faults and then erase DTC memory
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes