P2633 indicates that the PCM has detected a low voltage condition on the control circuit for fuel pump B. This usually means the signal that tells the pump to run is missing or too weak, which can prevent the pump from operating correctly.
The pump itself may have an internal short or open that pulls the control line low, or the integrated driver module within the pump assembly may have failed.
Damaged, chafed, or corroded wires in the fuel pump B control circuit can cause a low voltage reading; common points are connectors at the pump, chassis ground points, or along the harness.
If the fuse supplying power to the pump B control circuit is open or the relay fails to close, the PCM will see little or no voltage on the control line.
A loose or corroded ground strap or terminal can cause the control line to float low, triggering the code even if the pump and wiring are otherwise sound.
The transistor or driver inside the PCM that switches the fuel pump B control line can fail, though this is far less common than wiring or pump issues.
In rare cases, a corrupted PCM program may misinterpret normal circuit voltage as low; updating or re‑flashing the PCM may resolve the issue after hardware checks.
No. The PCM is rarely at fault for this code. The most common causes are wiring problems, a failed fuel pump B or its driver, or a blown fuse/relay. PCM replacement should only be considered after those components have been inspected and ruled out.
Clearing the code only turns off the Check Engine Light; if the underlying issue (e.g., a shorted wire or failing pump) remains, the code will return shortly after the vehicle is driven.
Yes. A loose or corroded connector in the fuel pump B control circuit can create an intermittent low‑voltage condition, leading to a code that sets sporadically or only under certain conditions such as engine vibration.
Driving with this code can be risky because the fuel pump may not receive the proper command to run, which can cause stalling, loss of power, or a no‑start condition. It is advisable to diagnose and repair the issue before relying on the vehicle for extended trips.