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.
1994 Audi 90 CS QuattroFACTORY OEM SERVICE PROCEDURE
Engine Sensors & Switches: Notes
NOTE:
Due to a production change, Cabriolet and 90 models are equipped with one of 2 different ECMs. Early version ECM can be identified by part number 4AO 906 266 A/AA/AB (MMS 200), referred to as ECM "A" in this article. Later version ECM can be identified by part number 8AO 906 266 B (MMS 300), referred to as ECM "B" in this article. 100 models use ECM "A".
Factory Service Tools
Use the Manual With the Right Hardware
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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.