C0091high severityChassis
Brake Booster Performance
on 2015 Kia Forte 1.8L I4 · FWD
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
- 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.
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Other Chassis codes on this vehicle
C0021
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C0022
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C0023
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C0024
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C0025
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C0026
RF Wheel Speed Sensor Circuit Intermittent
C0027
LR Wheel Speed Sensor Circuit Intermittent
C0028
RR Wheel Speed Sensor Circuit Intermittent
C0035
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C0036
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