Vehicles affected: 2005-’07 Buick Lacrosse 3.6L and 3.8L

Symptom: Transmission slip, transmission slip codes, transmission fluid burnt, low transmission line pressure, transmission failure.

Problem: The mass air flow (MAF) sensor elements may be dirty and causing lower than expected engine load calculation.

Test & Fix:
Determine if the vehicle is equipped with a MAF sensor. If the MAF sensor elements are coated with contaminants, such as oil and/or dirt, then the Powertrain Control Module (PCM) will not receive correct airflow/load input from the MAF sensor.

This usually causes a lean air/fuel condition, but also is known to cause lower than expected transmission line
pressure.

Most of the time, cleaning the sensor elements with a cotton swab and electrical contact or MAF cleaner will fix the incorrect MAF signal and allow transmission line pressure to return to normal.

GM has a bulletin, #04-07-30-013B, related to this condition, but refers only to aftermarket air filters as the cause. Many vehicles have been confirmed to have this condition with an OEM air filter.

Courtesy of Identifix, Inc.