Idle Speed Increase W/ Climate Control On

NOTE: For vehicles with all-wheel drive, if the heating or air conditioning needs increase, a positive voltage signal is sent from the climate control to the ECM. This positive voltage signal informs the ECM that the climate control system requires a higher idle speed to bring the interior temperature to desired level (whether heating or cooling is necessary). However the engine speed is not increased until the throttle is depressed once.

Test conditions
- Climate control functioning properly
- No malfunctions in climate control DTC memory
- Interior temperature greater than 15 °C
- Rear window defroster OFF

Test procedure
- Connect VAG 1551 or VAG 1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle).

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 HELP
Input display group number XXX

- Press buttons -0-, -5- and -0- to input display group number 50 (050), and press -Q- button to confirm input.

Indicated on display (1-4 display fields)

Read Measuring Value Block 50 ->
1 2 3 4

- Verify specification for idle speed adjustment.





- Activate climate control by pressing "AUTO" button.
Compressor must run.
- Set climate control to maximum heat or cooling (e.g. lowest temperature and highest fan position/Display field 3)
- Press accelerator pedal.





- Switch ignition off.

Checking circuitry





- Connect VAG 1598/22 test box to ECM harness connector.
- Check wiring from ECM terminal 10 to climate control for open circuit or short circuit.
- If wiring is OK, check climate control for correct operation.