With Manufacturer's Scan Tool

Signals to and from A/C System, checking

Special tools and equipment
- V.A.G 1551 scan tool (or VAG 1552 mobile scan tool) with VAG 1551/3B cable
- VAG 1598/31 adapter cable
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram

Test requirements
- The A/C system must function properly.
- A/C system must be switched off.
- There must not be any DTCs stored in DTC memory, checking DTC memory.
- Vehicle must be at room temperature (warmer than + 15 °C).

Test sequence
- Connect V.A.G 1551 scan tool (VAG 1552). Start engine and select the Engine Control Module (ECM) using address word 01.

Indicated on display:


Rapid data transfer HELP
Select function XX


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

Indicated on display:


Read measuring value block HELP
Enter display group number XXX


- Press buttons -0-, -5- and -0- to select "Display group number 50". Press -Q- button to confirm input.

Indicated on display: (1 to 4 = display fields)


Read measuring value block 50 ->
1 2 3 4


- Observe indication in display field 4. Compr.OFF must be indicated.
- Switch A/C system on.
- Set it to the lowest temperature and the highest fan setting.
Indication in display field 4 must switch to compr.ON.
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06. Press -Q- button to confirm input.
- Switch ignition off.

If reading does not change:







- Connect VAG 1598/31 adapter cable to control module wiring harness. Engine Control Module (ECM) is not connected.
- Check for open circuits in wires between test box socket 41 and A/C system according to wiring diagram. Wire resistance: max: 1.5 Ohms