P2633 critical

Fuel Pump B Control Circuit Low

The P2633 code means the vehicle's onboard diagnostic system has detected: Fuel Pump B Control Circuit Low. This is a critical severity code.

My Garage →

Keep driving?: No -- stop driving
DIY difficulty: hard
Estimated cost: $300 - $900 (parts and labor)

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Common Symptoms

Fuel pump B running at reduced speed
Low fuel supply pressure
Engine stalling under load
Hard starting especially when warm

Probable Causes (Ranked by Likelihood)

Short to ground in pump B control circuit Very High
Fuel pump B motor winding failure High
High-resistance connection at pump B connector Moderate
ECM pump B driver pulling low Low

Step-by-Step Diagnostic Procedure

Measure pump B circuit voltage at connector
Check pump B wiring for short to ground
Test pump B motor current draw
Inspect fuel tank connector for corrosion

Frequently Asked Questions

Why does my engine stall only under heavy load?

At light load the reduced pump B output may provide enough fuel, but under heavy acceleration the demand exceeds what the weakened pump can supply.

Can a corroded fuel tank connector cause P2633?

Yes. In-tank fuel pump connectors are exposed to fuel vapors and can corrode, causing high resistance that drops the voltage reaching the pump.

Is pump B the same as the lift pump?

In many applications, yes. The lift pump or transfer pump (pump B) is the low-pressure pump that feeds fuel from the tank to the high-pressure injection pump.