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
Airflow Meter
- Disconnect airflow meter. Turn ignition switch to RUN position. Ensure about 5 volts are present between harness side connector Gray/White wire and ground, Gray/White and Gray/Yellow, and Gray/White and Gray/Blue wires. If voltage is not correct, check continuity of wiring to MCU (in control box at right or left shock tower).
- If wiring is okay, replace MCU with a known good unit. If voltage is okay, ensure continuity is present between airflow meter terminal Nos. 2 and 4, and Nos. 2 and 3. If no continuity is indicated, replace airflow meter.
- Reconnect wiring harness to airflow meter. Remove wiring harness boot. Connect negative lead of a digital voltmeter to ground. Using the positive lead, carefully backprobe the Gray/Yellow wire on airflow meter.
- Check for voltage while opening and closing airflow meter measuring door. If voltage varies between .5 and 4.5 volt, airflow meter is okay, If voltage is not as specified, replace airflow meter.
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.
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