BMW Loss Of Brake Assist May Cause Increased Stopping Distances

In February 2021, BMW opened an investigation into certain BMW vehicles after receiving warranty claim reports involving damage to the oil/vacuum pump which supplies vacuum for brake assistance. Analyses were conducted to determine if the issue is related to certain vehicle models, oil/vacuum pump build level configurations, or vehicle operating conditions. Preliminary information suggested that engine management software could be involved. Further testing showed that certain pump parameter specifications, in combination with certain vehicle operating conditions (unusual engine start conditions caused by the vehicle operator), could cause a brief reverse rotation of the crankshaft and cause damage to the oil/vacuum pump.

Description of Defect: The safety recall involves engine management software that, under certain engine start conditions, could cause the oil/vacuum pump to become damaged. The specific engine start conditions consist of either

1) pressing the engine start/stop button two times in rapid succession, or

2) depressing the brake pedal very briefly while pressing the engine start/stop button.

This could result in a loss of brake assist. However, prior to a loss of brake assist, the full brake assist function is available for approximately two or three full brake applications, or approximately six partial brake applications. Fully mechanical braking (without assist) is not affected, and remains available.

Dealers will correct the problem by updating the engine management software. Owner notification letters are expected to be mailed October 1, 2021.