C0090moderate severityChassis
Brake Booster Pressure Sensor Circuit
on 2004 Subaru Legacy 3.0L H6 · AWD
What this code means
Malfunction in the brake booster vacuum or pressure sensor circuit.
Symptoms
- Brake warning light on
- Hard brake pedal
- Increased stopping distance
- Check Engine Light may also be on
Common causes
- Faulty brake booster pressure sensor
- Vacuum hose leak
- Wiring damage
- Brake booster vacuum pump failure on diesel/turbo vehicles
Diagnostic steps
- Test brake booster vacuum with gauge
- Check vacuum hose to booster
- Test pressure sensor signal
- Inspect wiring and connector
- Check engine vacuum source
Repair notes
Repair vacuum leak or replace pressure sensor. On diesel vehicles, check vacuum pump.
Other Chassis codes on this vehicle
C0021
LF Wheel Speed Sensor Range/Performance
C0022
RF Wheel Speed Sensor Range/Performance
C0023
LR Wheel Speed Sensor Range/Performance
C0024
RR Wheel Speed Sensor Range/Performance
C0025
LF Wheel Speed Sensor Circuit Intermittent
C0026
RF Wheel Speed Sensor Circuit Intermittent
C0027
LR Wheel Speed Sensor Circuit Intermittent
C0028
RR Wheel Speed Sensor Circuit Intermittent
C0035
Left Front Wheel Speed Sensor Circuit
C0036
Left Front Wheel Speed Signal Erratic