C027B Low Brake Pedal — Service Bulletin Fix
Why are you getting a C027B Low Brake Pedal code after replacing a master cylinder
GM has issued a service bulletin #PI0785B to address a C027B code that appears after replacing a master cylinder on the vehicles listed below. GM says the C027B trouble code is most likely due to a missing O-ring that fell off during the master cylinder replacement procedure. The missing O-ring results in a vacuum leak between the vacuum brake booster and the master cylinder causing a low brake pedal and the trouble code.
To prevent the problem from happening again, GM recommends bleeding the booster vacuum by pumping the brake pedal or pulling the check valve out of the booster before removing the master cylinder. The residual vacuum suction may be the culprit that dislodges the O-ring when pulling the master cylinder out.
2009-2014 Buick Enclave
2010-2012 Buick LaCrosse
2011-2014 Buick Regal
2012-2014 Buick Verano
2013-2014 Buick Encore
2009-2014 Cadillac CTS, SRX
2013-2014 Cadillac ATS, XTS
2009-2012 Chevrolet Colorado
2009-2014 Chevrolet Corvette, Impala, Malibu, Traverse
2010-2014 Chevrolet Camaro, Equinox
2011-2014 Chevrolet Cruze
2012 Chevrolet Captiva Sport
2012-2014 Chevrolet Sonic
2013-2014 Chevrolet Spark
2009-2012 GMC Canyon
2009-2014 GMC Acadia
2010-2014 GMC Terrain
Posted on by Rick Muscoplat