Idle Speed, Checking

Idle speed, checking


NOTES:
- Idle speed, ignition timing and CO-content cannot be adjusted.
- Idle speed is maintained by the throttle valve control module.
- CO-content is maintained and adjusted by Oxygen Sensor (O2S) control. Malfunctions in O2S control are recognized by On Board Diagnostic (OBD) and stored in DTC memory.

Required special tools and test equipment
VAG 1551 or VAG 1552 Scan Tool (ST) with VAG 1551/3 adapter cable

Test conditions
- Fuses for engine electronics OK
- No malfunctions stored in DTC memory
- Engine Coolant Temperature (ECT) at least 80 °(176 °)
- All electrical consumers switched off (radiator coolant fan must not run during test)
- A/C switched off
- Exhaust system free of leaks
- Automatic transmission selector lever in "P" or "N" position
- Throttle valve in Closed Throttle Position (CTP); for Accelerator Pedal (AP) cable adjustment:

Checking
- 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).[1][2]Scan Tool Connecting and Initial Checks

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -4- to select "Basic Setting" function 04, and press -Q- button to confirm input.

Indicated on display


System in Basic Setting 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)


System in Basic Setting 50 ->
1 2 3 4


NOTE:
After selecting function 04, the ECM initiates the following:
- EVAP canister purge regulator valve is closed
- A/C compressor is switched off
- Briefly raise engine speed (acceleration burst) and let engine run at idle for another 2 minutes.
- Compare display with specified values (display fields 1-4):

Display Group 50:

If displayed values are OK (as specified):
- Press -> button.
- Press buttons -0- and -6- to insert "End Output" address word 06, and press -Q- button to confirm input.
- Check readiness code.If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code.
Readiness Code Reading
Readiness Code, Generating


NOTE:
- For vehicles with front-wheel drive, increased idle speed is achieved if there is voltage (from terminal 15er) supplied to terminal 10 of the Engine Control Module (ECM).
- For vehicles with all-wheel drive, if the heating or air conditioning needs an increase in idle speed, 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 accelerator pedal is depressed once.
- Test the idle increase signal from the climate control. Testing and Inspection

Evaluation of display group 1, display field 1

Display Group 1: