P2633
Fuel Pump B Control Circuit Low
Fuel delivery
Generic OBD-II
High
What it means
P2633 means the PCM detected low voltage (usually a short to ground) in the control circuit for fuel pump B. Because this circuit switches or regulates a fuel pump, the fault can reduce or interrupt fuel delivery. That makes hard starting, stalling, no-start, or power loss likely until the wiring, relay, or pump is repaired.
High
Can I keep driving? Often not — a fault in the fuel pump control circuit can cut or reduce fuel delivery, causing stalling, no-start, or loss of power.
Common symptoms
What you'll notice
- Check-engine light on
- Hard starting, no-start, or stalling
- Loss of power or hesitation under load
- Engine cutting out at higher fuel demand
Common causes
Most likely first
- Short to ground or low voltage in the fuel pump control wiringLikely
- Failed fuel pump relay or driver moduleCommon
- Corroded or loose connector at the pump, relay, or PCMCommon
- Failing fuel pump BLess often
- Faulty PCM output circuit (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for related fuel-pump or fuel-pressure codes.
- Inspect the pump and relay connectors and wiring for a short to ground or corrosion.
- Test the fuel pump relay and confirm supply voltage and ground.
- Measure fuel pressure and command the pump with a scan tool.
- Replace the pump or relay if faulty; otherwise repair the wiring. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2633?+
No. A fuel pump control fault can leave you without enough fuel pressure and cause a stall or no-start with little warning. Have it diagnosed before depending on the vehicle.
Can I just clear P2633?+
It will return, and the fuel-delivery problems continue, until the circuit, relay, or pump is repaired. Clearing does not restore fuel pressure.
Related codes
Often seen with P2633
Read & clear P2633 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX