C0022: Brake Booster Solenoid
What to do
Your normal brakes are unaffected. What may have stopped working is automatic braking — emergency braking assistance, adaptive cruise, hill hold — so do not rely on those until it is fixed, and be aware they may not warn you that they are unavailable.
What this code means
The brake booster solenoid circuit has a fault.
This solenoid is what lets the car brake without the driver.
A conventional booster only multiplies what the pedal supplies — no pedal, no braking. Autonomous emergency braking, adaptive cruise control and hill hold all need the car to apply the brakes with the driver's foot elsewhere, and on a vacuum booster the solenoid is the part that does it: it admits atmospheric pressure to the booster chamber on command.
So the systems that fail with it are the driver-assistance ones, and they may go quiet without saying much. Do not assume automatic emergency braking is still available while this code is stored.
Ordinary braking is unaffected — the pedal still works through the same booster in the normal way.
Likely causes
Start here
- Corroded or loose connector · specialist
- Faulty brake booster solenoid · specialist
- Damaged wiring harness · specialist
Less common
- Open circuit in sensor wiring · specialist
- Faulty stability control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about C0022.