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.
1990 BMW 735iFACTORY OEM SERVICE PROCEDURE
Air Temperature Sensor
- Disconnect airflow meter. Turn ignition switch to RUN position. Check for 5 volts between Gray/Violet wire of harness side connector and ground. If no voltage is present, check continuity of wiring to MCU (in control box at right or left shock tower).
- If wiring is okay, MCU may be faulty. If voltage is okay, reconnect airflow meter and erase trouble code from MCU memory. Test drive vehicle and recheck for trouble code. If no code is present, the problem may be intermittent. See INTERMITTENTS in TESTS W/O CODES article. If code is still present, replace airflow meter.
- Erase trouble code from MCU memory. Test drive vehicle and recheck for trouble code. If code still present, replace MCU with a known good unit.
Factory Service Tools
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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.