Brake Booster Pressure Sensor Circuit
2012-2012 Subaru Legacy 3.6L H6
The 2012 Subaru Legacy is equipped with a 3.6L flat-6 engine. Below you'll find detailed c0090 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.
Description
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.
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
C0090 on Other Vehicles
Common Questions
What does code C0090 mean on a 2012-2012 Subaru Legacy?
C0090 stands for "Brake Booster Pressure Sensor Circuit". Malfunction in the brake booster vacuum or pressure sensor circuit.
What are the symptoms of C0090 on a Subaru Legacy?
Common symptoms of C0090 include: Brake warning light on, Hard brake pedal, Increased stopping distance, Check Engine Light may also be on.
What causes C0090 on a 2012-2012 Subaru Legacy?
Common causes of C0090 include: Faulty brake booster pressure sensor, Vacuum hose leak, Wiring damage, Brake booster vacuum pump failure on diesel/turbo vehicles.
Last updated: March 2026