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

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.

Vehicle Applications:  

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.

Courtesy of Identifix, Inc.

You May Also Like

BendPak Founder Don Henthorn Passes Away

Grew company from small machine shop to global leader in car lifts and garage equipment.

Don Henthorn, owner and founder of BendPak Inc., peacefully passed away at home Thursday, March 28, at the age of 85. Under his leadership, BendPak has grown from a small machine shop to one of the world’s leading manufacturers of car lifts and automotive service equipment.

Management and operations of the privately owned company are unchanged. 

Constant-Velocity Axle Options

Whether new or remanufactured, complete CV axle assemblies can throw you a curveball from time to time.

10 Timing Belt Tips

Here are the some key installation and service tips to make your next timing belt job just a little easier.

CVT Transmissions

The point here is not to fear a customer complaint about a CVT transmission. 

Mercedes 4MATIC Diagnostics

The Mercedes-Benz 4MATIC all-wheel drive (AWD) systems have been around for a while now.

Other Posts

Axle Torque Procedures

Guessing the correct torque setting is a bad idea.

Avoiding Brake Noise Comebacks

Brake systems are complex and require an understanding of the root cause of generating the noise.

Topology And Your Scan Tool

Topology influences how you access the modules with your scan tool.

Car properties detailed in "see proof" car image.
ASE Practice Tests Available Online

You can get a good idea of what to expect by adding the official ASE practice tests to their study plans.