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

Main Navigation

Advertisement
Social Connect
Resources
Our Brand Family
Underhood Service Logo
Technical resources to help diagnose and repair engine-related service issues.
Electronic

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.

Underhood Service Staff Writers
By Underhood Service Staff Writers
Published:

Vehicle Applications:  

Related Articles

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

Engine

Lifter Deactivation

The area of contact between the lifters and cam lobes is the highest loaded surface inside an engine.

Andrew Markel
By Andrew Markel
Andrew Markel is the director of content for Underhood Service magazine. He has been with Babcox Media for 20 years. He is a technician and former service writer and holds several automotive certifications from ASE and ­aftermarket manufacturers.
Published:

The basic function of a valve lifter is pretty simple. It sits on the camshaft and transfers the motions of the cam lobe up through the pushrods and rockers to open and close the valves. The size and shape of the cam lobe under the lifter (multiplied by the ratio of the rocker arms) determine valve lift and duration. As such, the lifter just follows the motions of the cam. But, it does play a role in valvetrain lash (clearance) and noise.

Read Full Article

More Electronic Posts
ECM Damage

Engineers have devised two strategies that can be called the “immune system” for the electrical system.

By Underhood Service Staff Writers
Voltage Drop Testing

The measurement of voltage is like the speed of the traffic.

By Andrew Markel
Spark Plug Fouling

Understanding why spark plugs get dirty.

By Andrew Markel
Understanding Stop/Start Charging and Starting Systems

The problem may not have been caused by a complicated reason, something simple may have caused the system not to work.

By Andrew Markel

Other Posts

Ignition Coil Output

To see inductance inside the primary windings, use an amp probe placed around the positive wire for the ignition coil.

By Andrew Markel
Caring For AGM And Flooded Car Batteries

Faulty battery cables, if loose, corroded, or damaged, can lead to power drainage.

By Underhood Service Staff Writers
Power Window Regulator and Motor Service

Power windows are great as long as they roll up and down when commanded to do so.

By Andrew Markel
Hybrid Vehicle Fluid Maintenance

There are opportunities your shop can’t pass up just because the car or SUV has a hybrid badge on the back.

By Andrew Markel