Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI1998A8 SEDAN (4D2) V8-3.7L (AEW)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSOXYGEN SENSORS (O2S)HEATED OXYGEN SENSOR (HO2S), CHECKING
1998 Audi A8 Sedan (4D2) V8-3.7L (AEW)
Heated Oxygen Sensor (HO2S), Checking
1998 Audi A8 Sedan (4D2) V8-3.7L (AEW)SECTION Heated Oxygen Sensor (HO2S), Checking
Heated Oxygen Sensor (HO2S), Checking
Requirements
- HO2S properly installed
- Exhaust system free of leaks
Checking
- Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). Refer "Scan Tool Testing/SCan Tool Connecting and Initial Checks/Connecting VAG1551 or VAG1551 Scan Tool" Testing and Inspection
Indicated on display
Rapid data transfer HELP
Select function XX
- 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
- Press buttons -0-, -0- and -3- to input display group number 3 (003), and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block 3 ->
1 2 3 4
- Check specified values for basic functions at engine idle speed (display field 3):
Continue checking only after engine coolant temperature in display field 3 has reached at least 85 °C (185 °F).
- Press -C- button.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Press buttons -0-, -2- and -6- to input display group number 26 (026), and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block 26 ->
1 2 3 4
- Check specified values for Heated Oxygen Sensors (HO2S and HO2S 2), display fields 1-4:
- Press -C- button.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.