With Manufacturer's Scan Tool

Idle, checking

NOTE:
- Idle speed, ignition timing, and CO content cannot be adjusted.
- Idle speed (RPM) is adjusted to a specified value by Engine Control Module (ECM).
- CO content is adjusted to a specified value by oxygen sensor control. Problems with the oxygen sensor control are recorded by the On Board Diagnostic (OBD) and stored in the DTC memory.

Test requirements

- EPC indicator lamp may not be switched on. Significance of EPC warning lamp. Refer to Description of On-Board Diagnostics/EPC Warning Lamp Operation EPC Warning Lamp Operation
- Parking brake must be engaged or else daylight driving lights will be switched on
- Exhaust system must be properly sealed between cylinder head and catalytic converter
- Coolant temp. at least 80 °C See Display group 04, display field 3
- All electrical consumers like, for example, lights and rear window heating must be switched off
- A/C system must be switched off
- For automatic transmission, selector lever must be in -P- or -N-

Test sequence

- Connect V.A.G 1551 scan tool (VAG 1552). Start engine and select Engine Control Module (ECM) using address word 01. Refer to Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting V.A.G 1551 Scan Tool [1][2][3]Connecting VAG 1551 Scan Tool
- Check DTC memory, repair malfunctions if necessary and then erase DTC memory, Erasing and checking DTC memory.
- Then:
- Connect Scan Tool (ST) V.A.G 1551
- Let engine continue to idle

Indicated on display

Rapid data transfer HELP
Select function XX

- Press 0 and 4 for the function "Basic Adjustment", and then press Q to exit from input mode.

Indicated on display

Basic Setting HELP
Input display group number XXX

Checking Idle Speed (RPM)

- Press 0, 5, and 6 for "Display Group No. 56", and then press Q to exit from input mode.

Indicated on display (1 - 4 = display fields)

System in Basic Setting 56 ->
1 2 3 4

- Check idle speed (RPM) in display field 1. Specified value
All-wheel drive: 620-740 RPM
Front-wheel drive: 710-860 RPM

NOTE: If engines of front-wheel drive vehicles run at 620-740 RPM, check control module coding.

- Press -> button.
- Press 0 and 6 for the function "End Output", and then press Q to exit from input mode.

If idle speed (RPM) is not obtained:
- Adapt Engine Control Module (ECM) to throttle valve control module.
- Perform a road test.

The following operating conditions must be obtained during road test:
- Coolant temperature must rise to above 80°C.
- Once the temperature is reached, the following conditions
idle
Partial throttle
Wide Open Throttle (WOT)
Deceleration mode must be reached several times each.
- Engine speed must be increased to above 3500 RPM during Wide Open Throttle (WOT).
- Check control module's DTC memory again.
- Test operating conditions of engine. Engine Operating Conditions, Checking
- Repeat idle test.

If expected values are still not obtained:
- Test throttle valve control module. Testing and Inspection

If no DTC can be found here:
- Test Heated Oxygen Sensors (HO2S) and oxygen sensor control. Refer to Oxygen Sensor Before Catalyst, Checking/Sensors and Control Check Testing and Inspection
- Check intake system for unmetered air. Testing and Inspection