Code C0587 indicates an open circuit in the brake booster motor position sensor circuit. The sensor tells the vehicle's control module the position of the brake booster motor; when the signal is lost, the module sets this fault and may limit power‑brake assist.
The sensor itself has an internal open circuit or short, preventing it from sending a position signal to the control module.
Damaged wiring, a broken wire, or corrosion at the sensor or module connector interrupts the signal path.
If the motor seizes or fails, it may not move the sensor mechanism, resulting in a lack of position change and an apparent open circuit.
Inadequate ground connection or insufficient voltage at the sensor can cause the control module to interpret the circuit as open.
A fault inside the powertrain control module that prevents it from reading the sensor signal is possible but uncommon; other causes should be ruled out first.
No. Replacing the control module is rarely needed for this code; the sensor, its wiring, or the brake booster motor are far more likely culprits. The PCM should only be considered after those components have been verified as good.
A blown fuse that supplies power to the brake booster motor or its sensor can produce an open‑circuit condition, so checking the relevant fuse is an early diagnostic step.
The vehicle’s base hydraulic brakes will still function, but power‑brake assist may be reduced or unavailable, resulting in a harder pedal feel and longer stopping distances.