C0090
ChassisBrake Systemmoderate severityBrake Booster Pressure Sensor Circuit
What C0090 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
Where to start: Repair vacuum leak or replace pressure sensor. On diesel vehicles, check vacuum pump.
🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
Enhanced codes (ABS, airbag, TPMS) plus repair reports.
SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.
Related Codes
Community Confirmed Fixes
No confirmed fixes yet for this code. Be the first to contribute!
Submit a FixFound a Fix for C0090?
Help other technicians by sharing what worked on your vehicle.
Submit Your Fix