With Manufacturer's Scan Tool

Idle Speed, Checking

Special tools and equipment







- VAS5051 with VAG5051/1

Test requirements
- Exhaust system free of leaks.
- Coolant temperature at least 80 degree C.
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- No pressure gauges (e.g. for fuel pressure test) connected.

NOTE:
- Idle speed cannot be adjusted.
- Idle speed is checked during basic setting of Engine.
- During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve -N80- is closed and A/C compressor is switched off

Test sequence
- Connect VAS 5051 and select "01 engine electrical. The engine must be running at idle. Connecting VAS 5051/VAG 1551 Scan Tool (ST)
- Check DTC Memory. There must not be any DTCs stored. Repair malfunctions if necessary, erase DTC memory, switch engine off and start again, road test vehicle and check DTC memory again as a control measure. With Manufacturer's Scan Tool
- Let engine continue to run at idle.

CAUTION: Electric radiator fan must not run.

Display on VAS 5051:







- Under -1- select diagnostic function "04 - Basic setting".

Display on VAS 5051:







1 - Enter display group, max. entered value = 255
- Enter "056" for "display group number 056" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS 5051:







- Check whether engine speed (RPM) in display field -1- (actual speed) is within permitted tolerance range.

Display Group 056:

NOTE:
- Engine speed in display field 1 (actual engine speed) is current engine speed.
- Engine speed in display field 2 (specified engine speed) is a theoretical engine speed calculated by ECM.
- At idle, the ECM always attempts to adapt engine speed (actual) to specified engine speed (specified).
- This means that engine speed (actual) must always approximately match engine speed (specified) at idle.
- Display fields 3 and 4 provide information, but are not relevant for checking idle speed.

Display on VAS 5051:







If the specified value is obtained:
- Exit function "04 - Basic setting" by pressing <- button.

If specified value is not obtained:
- Check DTC memory again. With Manufacturer's Scan Tool
- If DTC memory has been erased, generate readiness code Readiness Code, Generating

If idle speed is too high or low and there are no DTCs in DTC memory, the following tests (marked with dots) must be performed:
- False air in intake air system. Testing and Inspection
- Check throttle valve control module. Throttle Valve Control Module -J338-, Checking
- Evaporative Emission (EVAP) canister purge regulator valve always open. Testing and Inspection
- Perform adaptation of throttle valve control module. Throttle Valve Control Module -J338-, Adapting