Mystery MIL

Feb. 10, 2020

This bulletin applies to 2014-2018 Buick Regal and 2017-2018 Envision vehicles, equipped with a 2.5L or 2.0L engine. The MIL may be on, with no drivability issues. DTC P2097 may be stored. There are many things that can cause P2097 and care must be taken when diagnosing this code.

Failure to follow SI diagnostics first may lead to misdiagnosis of P0297. SI diagnostics for P0297 tests the purge valve and lines for concerns. When performing the procedures below, the purge solenoid vacuum source line should be disconnected and blocked off at the intake manifold vacuum source.

Follow SI diagnostics first. If this does not lead to a resolution, perform the following:

1. Idle the engine in Park with your foot off of the brake pedal.

2. Idle with your foot on the brake pedal to hold the vehicle from moving. Place the transmission into Drive.

3. Drive the vehicle at a steady speed of 50 mph or above without using the cruise control.

After completing the above, in the service bay with the vehicle in Park, take note of the long term fuel trim value. Using your foot on the accelerator pedal, raise engine idle up to approximately 2,000 rpm and hold it there for 2 minutes and monitor any changes in the long term fuel trim value.

If the long term fuel trim value was high and then dropped into a normal range (-13% to +13%) and stays there, the concern may be a vacuum leak, skewed MAF sensor, modified/damaged air box or a non-OEM air filter. Swap as many parts from a known good vehicle to rule out specific components mentioned. If no change is found, perform an AFIT test on all fuel injectors to see if any lean injectors can be found. If no individual lean injectors are found, replace all four injectors.

If the long term fuel trim value was in a normal range (-13% to +13%) and never stayed outside of the normal range, ask the customer if they drive in heavy stop and go city traffic.

Drive with the customer to see if they are a “digital” driver. A digital driver is one who gets up to their desired speed, then lets off of the throttle and lets the vehicle coast down a few miles per hour, then gets back onto the throttle to get back up to the desired speed, and they continue to drive in this manner. This driving habit can induce P2097. If this is the case, the driver needs to change their driving style.