Brake Booster Performance
2011-2011 Mitsubishi Lancer 2.4L I4
The 2011 Mitsubishi Lancer is equipped with a 2.4L inline-4 engine. Below you'll find detailed c0091 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.
Description
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
- Perform brake booster leak-down test
- Check vacuum hose and check valve
- Test engine vacuum at idle
- Apply brakes with engine off then start engine (pedal should drop)
- Check booster operating rod adjustment
Repair Notes
Replace brake booster if diaphragm is leaking. Replace vacuum hose or check valve as needed.
Related Codes
Other Chassis Codes
- C0021LF Wheel Speed Sensor Range/Performance
- C0022RF Wheel Speed Sensor Range/Performance
- C0023LR Wheel Speed Sensor Range/Performance
- C0024RR Wheel Speed Sensor Range/Performance
- C0025LF Wheel Speed Sensor Circuit Intermittent
- C0026RF Wheel Speed Sensor Circuit Intermittent
- C0027LR Wheel Speed Sensor Circuit Intermittent
- C0028RR Wheel Speed Sensor Circuit Intermittent
- C0035Left Front Wheel Speed Sensor Circuit
- C0036Left Front Wheel Speed Signal Erratic
C0091 on Other Vehicles
Mitsubishi 3000GT
1996-1996 3.0L V6 Twin Turbo
Mitsubishi 3000GT
1997-1997 3.0L V6 Twin Turbo
Mitsubishi 3000GT
1998-1998 3.0L V6 Twin Turbo
Mitsubishi 3000GT
1999-1999 3.0L V6 Twin Turbo
Mitsubishi Colt JP
2002-2002 1.3L I4 4A90
Mitsubishi Colt JP
2002-2002 1.5L I4 4A91
Mitsubishi Colt JP
2003-2003 1.3L I4 4A90
Mitsubishi Colt JP
2003-2003 1.5L I4 4A91
Common Questions
What does code C0091 mean on a 2011-2011 Mitsubishi Lancer?
C0091 stands for "Brake Booster Performance". The brake booster is not providing adequate assist, detected by pressure sensor or pedal effort monitoring.
What are the symptoms of C0091 on a Mitsubishi Lancer?
Common symptoms of C0091 include: Hard brake pedal, Increased stopping distance, Brake warning light on, Engine may stall when brakes applied firmly.
What causes C0091 on a 2011-2011 Mitsubishi Lancer?
Common causes of C0091 include: Leaking brake booster diaphragm, Cracked or disconnected vacuum hose, Check valve failure, Brake booster control valve stuck, Low engine vacuum on turbocharged vehicles.
Last updated: March 2026