Hard brake pedal after disconnecting battery
If you have a hard brake pedal after disconnecting the battery on the following two-mode hybrid vehicles, this may be your fix.
2008-10 Chevy Tahoe and GMC Yukons
2009-10 Cadillac Escalade, Chevy Silverado and GMC Sierra.
The braking systems on these vehicles require a one full minute power down before disconnecting the battery. If you turn the key to the accessory position or depress the brake pedal within the one-minute time frame, you can also cause the problem.
To fix the problem, simply disconnect and then reconnect the negative battery cable. Then start the engine and shut if off. Do not turn it to the accessory position. Wait one full minute without touching the brake pedal or key.
If you have trouble codes C121D 00 or C056D 00 stored, simply clear them with your code reader or scan tool.Posted on by Rick Muscoplat