What this code means

The brake booster is not providing adequate assist, detected by pressure sensor or pedal effort monitoring.

Symptoms

• Hard brake pedal
• Increased stopping distance
• Brake warning light on
• Engine may stall when brakes applied firmly

Common causes

• Leaking brake booster diaphragm
• Cracked or disconnected vacuum hose
• Check valve failure
• Brake booster control valve stuck
• Low engine vacuum on turbocharged vehicles

Diagnostic steps

1. Perform brake booster leak-down test
2. Check vacuum hose and check valve
3. Test engine vacuum at idle
4. Apply brakes with engine off then start engine (pedal should drop)
5. Check booster operating rod adjustment

Repair notes

Replace brake booster if diaphragm is leaking. Replace vacuum hose or check valve as needed.

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