Brake Assist Vacuum Too Low
The ECU monitors the vacuum supplied to the brake booster (either via a dedicated sensor or via intake manifold pressure). The level has dropped below the calibrated threshold; brake-pedal feel will be hard, and an electric vacuum pump may be commanded to restore vacuum.
Affected components
- Brake booster
- Vacuum pump
- Vacuum check valve
Common causes
- High likelihood: Vacuum leak in booster line or check valve
- Medium likelihood: Electric vacuum pump weak
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.