Idle Speed, Checking
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
- VAG1551 scan tool (or VAG1552 mobile scan tool) with VAG1551/3B cable
Test requirements
- Exhaust system must be properly sealed between catalytic converter and cylinder head.
- 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".
- Coolant temperature must be at least 85 °C See display group 04, display field 3
- Intake Air Temperature (IAT) less than 60 °C See Display group 04, display field 4
Test sequence
- Connect VAG1551 scan tool (VAG1552). 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 " Testing and Inspection
- Check DTC memory, repair any malfunctions and then erase DTC memory.
- Then:
- Connect Scan Tool (ST) VAG1551
- 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
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 Evaporative Emission (EVAP) canister purge regulator valve -N80- and the A/C compressor is switched off.
- Check adjustment requirements for basic setting in display field 4: Specification: 1x111111 Significance of numbers.
- 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 54 as follows:
- Press -C- button.
- Press 0, 5 and 4 for the function "display group number 54", and then press Q to exit from input mode.
Indicated on display: (1 to 4 = display fields)
System in basic setting 54 ->
1 2 3 4
NOTE: During the function "System in basic setting", the Evaporative Emission (EVAP) canister purge regulator valve -N80- and the A/C compressor is switched off.
Display Group 54:
- Check specified values for idle in display fields 1 through 4.
If specified values are still not obtained:
- Perform a road test.
- Check control module's DTC memory again.
- Repeat idle test.
If specified values are still not obtained:
- Check throttle valve control module. Testing and Inspection
- Test operating conditions of engine. Refer to Computers and Control Systems/Procedures/Operating Conditions of an Engine, Checking. Testing and Inspection
- Check intake system for unmetered air. Testing and Inspection
After successful repair:
- Read readiness code. If DTC memory was erased or the Engine Control Module (ECM) was disconnected from the continuous B+ supply, the readiness code must be re-generated. Refer to Monitors, Trip and/or Drive Cycle (Readiness Codes)/Reading Readiness Code. Testing and Inspection Refer to Monitors, Trip and/or Drive Cycle (Readiness Codes)/Generating Readiness Code. Testing and Inspection