Idle Speed: Testing and Inspection

Idle test


NOTE:
- Idle speed (RPM), ignition timing, and CO content cannot be adjusted.
- Idle speed is regulated to the specified value by the throttle valve actuator in connection with the DLS function.
- CO content is adjusted to a specified value by oxygen sensor control. Problems with the oxygen sensor control are recognized by On Board Diagnostic (OBD) and stored in DTC memory.


Special tools and equipment
- V.A.G 1551 scan tool (or VAG 1552 mobile scan tool) with VAG 1551/3B cable

Test requirements
- Exhaust system must be properly sealed between cylinder head and catalytic converter.
- Coolant temperature must be 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
- If vehicle is equipped with an A/C system, it must be switched off.
- For vehicles with 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 the Engine Control Module (ECM) using address word 01. (connecting scan tool and selecting ECM). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551 Scan Tool", Testing and Inspection
- Check DTC memory, repair any malfunctions and then erase DTC memory, Checking and erasing 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 buttons -0- and -4- to select "Basic Setting" function 04. Press -Q- button to confirm input.

Indicated on display:


Basic setting HELP
Enter display group number XXX


- Press buttons -0-, -0- and -1- to select "Display group number 1". Press -Q- button to confirm input.

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


System in basic setting 1 ->
1 2 3 4


NOTE: During the function "System in basic setting", the A/C compressor is switched off.


- Check adjustment requirements for basic setting in display field 4: Specification: 1x111111 Significance of numbers. Refer to "Scan Tool Testing/Measuring Value Blocks/Display Groups 0 to 9 - Basic Functions-". Refer to "Scan Tool Testing/Measuring Value Blocks (Function 08)/Evaluating Measured Value Blocks/Evaluating Display Groups 0 to 9", Testing and Inspection
- Increase engine speed briefly (depress accelerator quickly) and then let engine run at idle for 2 more minutes.

Checking idle speed (RPM)
- Change to display group 56 as follows:
- Press -C- button.
- Press buttons -0-, -5- and -6- to select "Display group number 56". Press -Q- button to confirm input.

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


System in basic setting 56 ->
1 2 3 4


- Check operational readiness in display field 4. Specification: 0x000 (Significance). Refer to "Scan Tool Testing/Measuring Value Blocks/Display Groups 50 to 69 -RPM Regulation-". Refer to "Scan Tool Testing/Measuring Value Blocks/Display Groups 0 to 9 - Basic Functions-". Refer to "Scan Tool Testing/Measuring Value Blocks (Function 08)/Evaluating Measured Value Blocks/Evaluating Display Groups 50 to 69", Testing and Inspection
- Check specified idle speed (RPM) in display field 2. Specification: 800 RPM
- Check idle speed (RPM) in display field 1. Specification: 740 to 920 RPM


NOTE: During the idle test, the A/C system is turned off and adaptation is performed for oxygen sensor control.


- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.

If idle speed (RPM) is not obtained:
- Adapt Engine Control Module (ECM) to throttle valve control module.
- Perform a road test.
- Check control module's DTC memory again.
- Repeat idle test.

If specified values are still not obtained:
- Check the throttle valve control module. Testing and Inspection
- Test operating conditions of engine. Refer to "Scan Tool Testing/Measuring Value Blocks (Function 08)/Evaluating Measured Value Blocks/Operating Conditions of Engine, Checking", Testing and Inspection
- Check intake system for false air. Testing and Inspection