BMW said that some of its 3-series cars and X5 SUVs may run roughly and illuminate the Check Engine light, storing trouble code P102 in computer memory in the process. One possible cause, the German carmaker reported, is an out-of-spec airflow meter signal.
To find out for sure, connect a DVOM, start the engine and test for battery voltage on the red/white at the airflow meter. Next, perform a voltage drop test on the ground (black) wire. Anything more than a 50mV drop is cause for concern. Finally, test the output signal on the yellow wire at the airflow meter. It should be .7 to .9 volt at idle.
If everything tests okay to this point, hook up your scan tool, go to the data stream and observe the grams/sec PID on the display. You should see approximately 5 grams/sec with the engine idling in Park, and greater than 150 grams/sec at wide open throttle above 5000 rpm. If the output isn't as specified, replace the airflow meter.
Vehicles that are susceptible to the airflow meter troubles are 2002 325xi Sport Wagons with 2.5-liter engines, 2002 330xi and X5s with 3.0-liter engines and 2004 330ci and 330i cars, also with 3.0-liter engines.
Volvo reports that the climate control panels on some of its 2001 S40 and V40 models may cease to function. According to the Swedish carmaker, the problem is often intermittent, and is due to voltage spikes being introduced into the panel by the blower motor. Installing a specially designed adapter harness with a built-in diode, part No. 30858845, between the blower motor and its connector should eliminate further trouble.
Some 2006 Chrysler 300 and Dodge Magnum and Charger models with 5.7-liter engines built before 9/3/05 may turn on the Check Engine light on initial start-up and store trouble code P2112 in the PCM. According to Chrysler, if there are no drivability symptoms associated with the code it's probably bogus, and caused by software issues in the PCM. Flashing the module with an updated calibration is the only surefire fix. Check with a dealer for the specifics of the reprogramming job.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].