C0022 is a chassis diagnostic trouble code that indicates a malfunction in the brake booster solenoid circuit. The brake booster solenoid regulates vacuum delivery to the power brake booster, and a fault can reduce or eliminate brake assist. The code is typically read with a scan tool capable of accessing chassis or ABS-related modules rather than just the engine PCM.
The vacuum regulator or booster control solenoid itself is the most common failure point, often due to internal wear, contamination, or an open coil winding.
Damaged wiring, chafed insulation, corroded terminals, or loose connectors between the solenoid and its controlling module are common, especially in vehicles exposed to under-hood heat and moisture.
Cracked vacuum hoses, a failed check valve, or a leaking booster diaphragm can prevent the system from reaching expected vacuum levels and trigger the code.
An internal leak in the brake booster itself can mimic a solenoid fault and is often identified only after the solenoid and its wiring are ruled out.
In rare cases, an internal driver issue in the module that commands the solenoid can prevent proper operation, but this is uncommon and should only be considered after the solenoid, wiring, and vacuum system are eliminated.
Driving with reduced brake assist increases stopping distance and risk. If the brake pedal feels unusually hard, the vehicle should be inspected before being driven extensively.
No. The PCM is almost never the cause of this code. Drivers are sometimes told to replace the computer, but the brake booster solenoid, its wiring, and the vacuum system are the typical culprits, and the PCM should only be considered after those have been thoroughly tested.
Yes. Many brake booster solenoid codes are set because the system cannot reach the expected vacuum level, so a leak in the booster hose or check valve can trigger the same fault as a bad solenoid.
No. Clearing the code only erases the stored fault. If the underlying condition is still present, the code will return and the braking concern will remain.