Diagnostic Trouble Code
P2633
Fuel Pump "B" Control Circuit Low — Generic OBD-II
What the code means
The control module has detected a low electrical condition in the Fuel Pump B control circuit.
The generic SAE definition of P2633 is Fuel Pump "B" Control Circuit Low.
This is an electrical control-circuit fault and is separate from the Mercedes charge-air interpretation of 2633 shown elsewhere on this page.
The word low describes the electrical condition detected in the control circuit. It does not by itself prove that the fuel pump has mechanically failed.
Possible causes
What could cause this P2633 fault?
Short to ground in the control circuit
Damaged wiring or connector
Poor electrical connection
Fuel-pump relay or control-device fault
Fuel-pump control-module fault
Power supply or ground problem
Fuel-pump electrical fault
Control-module output or monitoring fault
Diagnostic approach
What should you check?
- 1. Confirm the exact fault description. Make sure the vehicle is actually reporting Fuel Pump "B" Control Circuit Low rather than a manufacturer-specific P2633 definition.
- 2. Read all related fault codes. Check for additional fuel-system, voltage or control-module faults that may provide useful context.
- 3. Check the circuit before the pump. Inspect wiring, connectors, power supplies, grounds and the appropriate control or relay arrangement for the vehicle.
- 4. Test the electrical command. Use appropriate electrical tests and vehicle information to establish why the control circuit is being detected low.
- 5. Prove the failed component. Do not replace the fuel pump solely because P2633 is stored. Establish whether the fault lies in the pump, wiring, relay, control module or another part of the circuit.
A useful thing to remember
Always use the exact diagnostic description and vehicle application alongside the code number. P2633 is a good example of why the number alone may not tell the whole story.