What this code means

The electric brake vacuum pump that maintains brake boost during engine-off periods in start-stop systems is not providing adequate vacuum.

Symptoms

• Start-stop disabled
• Firm brake pedal during engine stop
• Brake assist warning
• Start-stop inhibited due to brake system
• Hard pedal after one or two stops

Common causes

• Electric vacuum pump motor weak
• Check valve in vacuum line leaking
• Vacuum line crack or disconnect
• Pump control module fault
• Brake booster diaphragm leak

Diagnostic steps

1. Monitor brake vacuum level during engine-off events
2. Test electric vacuum pump operation
3. Check vacuum lines and check valves
4. Measure vacuum decay rate with engine off
5. Test brake booster for leaks

Repair notes

Replace electric vacuum pump or check valve. Repair vacuum line leaks. Ensure brake boost is adequate during engine-off periods.

Other Powertrain codes on this vehicle