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 MANUALSAUDI199590 QUATTRO SPORT V6-2.8L (AAH)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSOXYGEN SENSORTESTING AND INSPECTIONELECTRICAL TESTING
1995 Audi 90 Quattro Sport V6-2.8L (AAH)
Electrical Testing
1995 Audi 90 Quattro Sport V6-2.8L (AAH)SECTION Electrical Testing
SENSOR ELECTRICAL TESTS:
- Disconnect harness connector for Heated Oxygen Sensor (HO2S) signal wire.
- Connect multimeter(Fluke 83 or equivalent) between oxygen sensor signal wire and GND.
^ Specified value: infinite ohms (no continuity).
If NO:
- Replace HO2S.
If YES:
- Switch multimeter to 0-2 volts measuring range and connect between signal wire connector (to ECM) and GND.
- Switch ignition ON.
^ Specified value: 400 +/- 50 mV.
If YES:
- Check wiring to ECM.
WIRING CHECKS:
- Switch ignition OFF.
- Connect VAG 1598 test box to ECM wiring harness using VAG 1598/11 adapter harness.
- Adapter harness for ECM is not connected.
- Check for continuity between Heated Oxygen Sensor (HO2S) 1 G39 signal wire and test box socket 50.
^ Specified value: maximum 1 ohm.
- Check for continuity between H02S 2 G108 signal wire and test box socket 48.
^ Specified value: maximum 1 ohm.
If specified values are not obtained:
- Repair open or short circuit in wiring connection between connector in engine compartment and ECM connector A terminal 50 and/or 48, according to wiring diagrams.
If there is no malfunction in wiring connection:
- Replace ECM.
- Disconnect harness connector for Heated Oxygen Sensor (HO2S) signal wire.
- Connect multimeter(Fluke 83 or equivalent) between oxygen sensor signal wire and GND.
^ Specified value: infinite ohms (no continuity).
If NO:
- Replace HO2S.
If YES:
- Switch multimeter to 0-2 volts measuring range and connect between signal wire connector (to ECM) and GND.
- Switch ignition ON.
^ Specified value: 400 +/- 50 mV.
If YES:
- Check wiring to ECM.
WIRING CHECKS:
- Switch ignition OFF.
- Connect VAG 1598 test box to ECM wiring harness using VAG 1598/11 adapter harness.
- Adapter harness for ECM is not connected.
Engine Control Module (ECM) Connectors:
- Check for continuity between Heated Oxygen Sensor (HO2S) 1 G39 signal wire and test box socket 50.
^ Specified value: maximum 1 ohm.
- Check for continuity between H02S 2 G108 signal wire and test box socket 48.
^ Specified value: maximum 1 ohm.
If specified values are not obtained:
- Repair open or short circuit in wiring connection between connector in engine compartment and ECM connector A terminal 50 and/or 48, according to wiring diagrams.
If there is no malfunction in wiring connection:
- Replace ECM.
RENDER: 1.0x
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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.