Tech Tip: BMW Check Engine Light On and Vehicle Running Rough Due to Airflow Meter
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Tech Tip: BMW Check Engine Light On and Vehicle Running Rough Due to Airflow Meter

If a customer complains of a check engine light on and a vehicle running rough, it may be due to problems with the airflow meter and wiring.

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Vehicle Applications:  

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2002 325XI Sport Wagon 2.5L, Eng Des M54; 330XI 3.0L; and X5 3.0L, Eng Cfg L6, Eng Des M54; and 2004 330CI 3.0L and 330I 3.0L

Customer Concern: Check engine light is on and the vehicle is running rough.

Potential Causes: Airflow Meter and Wiring

Tech Tips: Fault code points to airflow meter problems

Diagnostic Codes: P102

Tests/Procedures:

1. At the airflow meter, test for battery voltage on the red/white wire with the ignition on or engine running.

2. Check for ground on the black wire.

3. Test the output signal on the yellow wire. It should be approximately 0.7 to 0.9V at idle.

4. Use a scan tool to monitor the fuel trim numbers and the airflow meter data stream grams/sec readings. Nominal values are 5 grams/sec at idle in Park, and >150 at wide open throttle and 5,000 rpm under load. Some scan tools have a freeze-frame feature, which is useful in troubleshooting if the problem is set at idle versus at cruise.

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Courtesy of Identifix, Inc.

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