A8 Sedan V8-3.7L (AEW) (1997)
Idle Speed: Testing and Inspection
Engine Idle Speed And CO Content, Checking
NOTE:
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The engine idle speed, ignition timing and CO content are not adjustable.
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Engine idle speed is maintained at a specified value by the Idle Air Control (IAC) valve and the digital idle speed stabilization function of the
ECM.
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CO content is maintained at a specified value by Oxygen Sensor (O2S) control. Malfunctions in O2S control are detected by the On Board
Diagnostic (OBD) system and stored in Diagnostic Trouble Code (DTC) memory.
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Checking CO content before the Three Way Catalytic Converters (TWC) is not possible.
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When the ECM or the battery is disconnected, all learned values will be erased.
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Engine basic settings. Refer to "Scan Tool Testing/Basic Setting, (Function 04)" See: Powertrain Management/Computers and Control
Systems/Testing and Inspection
Requirements
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Engine coolant temperature at least 85°C (185 °F)
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All electrical consumers switched off (radiator coolant fan must not be running while checking idle speed)
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A/C switched off
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Automatic transmission selector lever in P or N position.
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Connect VAG1551 orVAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at
idle). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1551 or VAG1552 Scan Tool" See: Powertrain
Management/Computers and Control Systems/Testing and Inspection
CAUTION!
The radiator coolant fan must not run.
Indicated on display
Rapid data transfer
HELP
Select function XX
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Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block
Input display group number XXX
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Press buttons -0-, -0- and -5- to input display group number 5 (005), and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block 5
->
1
2
3
4
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Check specified engine idle speed values (display fields 1-2).