P2634 moderate

Fuel Pump B Control Circuit High

The P2634 code means the vehicle's onboard diagnostic system has detected: Fuel Pump B Control Circuit High. This is a moderate severity code.

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Keep driving?
Short distances only
DIY difficulty
hard
Estimated cost
$200 - $700 (parts and labor)
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Common Symptoms

  • Fuel pump B running at full speed constantly
  • Higher than normal fuel supply pressure
  • Fuel system noise from tank area
  • Check engine light on

Probable Causes (Ranked by Likelihood)

  • Short to voltage in pump B circuit Very High
  • Pump B relay stuck closed High
  • ECM pump B driver stuck high Moderate
  • Fuel pump control module failure Low

Step-by-Step Diagnostic Procedure

  1. Check pump B circuit for constant voltage

  2. Test pump B relay contacts

  3. Verify ECM can modulate pump speed

  4. Check fuel pump control module if equipped

Frequently Asked Questions

Can constant full-speed pump operation cause issues?

Yes. Excessive fuel supply pressure can overwhelm the high-pressure pump and fuel pressure regulator, and the constant operation increases pump wear and noise.

What is a fuel pump control module?

Some vehicles have a separate module that varies fuel pump speed based on demand. It sits between the ECM and the pump, using PWM to control pump voltage.

Will P2634 affect fuel economy?

Slightly. The constant high-speed pump operation wastes energy and can cause excess fuel to recirculate, reducing overall system efficiency.

Sources

This page is built from documented references. Verify against your own service info before repair work.

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