C0045: Brake Pressure Sensor B
What to do
The ordinary brakes are unaffected — what has switched off is the system that catches a skid for you. The car will feel completely normal until the moment it would have intervened, which is exactly when you will not want it missing. Drive gently in the wet and cold and get it diagnosed.
What this code means
Brake pressure sensor B has a circuit fault.
Brake pressure sensors let the module know how hard you are braking, in units it can act on.
Stability control needs the number. To decide whether to add brake pressure at one wheel it has to know what pressure is already there — and to add pressure with the pedal untouched it needs to know it succeeded. Hill-hold, autonomous braking and regenerative blending all read the same sensor.
A pressure sensor is threaded into the hydraulic circuit, usually in the modulator, so replacing one opens the brake system and the brakes must be bled afterwards. That is why it is a specialist job on a part that looks trivial.
The most important thing first: the car still stops.
ABS, traction control and stability control are all additions to a braking system that works without them. When the module finds a fault it switches itself off and hands back a conventional, fully hydraulic brake system — the pedal, the master cylinder, the lines and the calipers are untouched. You have not lost your brakes.
What you have lost is the help. Without ABS the wheels can lock under hard braking, which lengthens the stopping distance on a slippery surface and — the part people forget — takes away your ability to steer while braking hard, because a locked wheel cannot generate cornering force. Without stability control the car will not catch a slide for you.
So drive it, but drive it as though it were forty years old: brake earlier, leave more room, and be especially careful in rain, snow and on gravel.
Likely causes
Start here
- Faulty brake pressure sensor · specialist
- Corroded or loose connector · specialist
- Damaged wiring harness · specialist
Less common
- Open circuit in sensor wiring · specialist
- Faulty stability control module · specialist
Symptoms
Components involved
Information, not instruction
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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
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