A8 Sedan V8-3.7L (AEW) (1997)
Air/Fuel Mixture: Testing and Inspection
NOTES:
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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 "Diagnosis With Scan Tool, Address Word 01" at "On-Board Diagnostics II". See: 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.
PROCEDURE:
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Connect VAG 1551 (VAG 1552) Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at
idle). Refer to "How to Display and Read Diagnostic Trouble Codes" at "On-Board Diagnostics II". See: 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, 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).
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Press -> button to advance program sequence.
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Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.