Idle Speed Increase With Climate Control Switched on, Checking
Idle speed increase with climate control switched on, checking
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 a 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 (59° F)
- 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).Refer to "Scan tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551/VAG 1552 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 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.
Display Group 50:
- 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.
Display Group 50:
- Switch ignition off.
Checking circuitry
- Connect VAG 1598/22 test box to ECM harness connector.Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/22 Test Box" Testing and Inspection
- 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.