AutoCodes – GMC – P2636 GMC

P2636 GMC Code - Fuel Pump 'B' Low Flow/Performance

Quick Answer

The fuel pump is located on the left frame rail between the fuel tanks. Common causes include Faulty fuel pump relay, Faulty fuel pump, Fuel pump harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P2636 GMC indicates Fuel Pump 'B' Low Flow/Performance.
Common causes: Common causes include Faulty fuel pump relay, Faulty fuel pump, Fuel pump harness is open or shorted.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 16,913

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 01, 2020

Description
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
Comments
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Code P2636 GMC Description

The fuel pump is located on the left frame rail between the fuel tanks. The Engine Control Module (ECM) provides ignition positive voltage to the coil side of the fuel pump relay. The ECM energizes the fuel pump relay, which applies power to the fuel pump. Fuel is transferred from the rear fuel tank to the front fuel tank in order to ensure all of the usable fuel volume is available to the engine. This Diagnostic Trouble Code (DTC) sets when the ECM commands the transfer fuel pump ON and a predetermined change in the front and rear fuel level sensors does not occur.

OBDII Code P2636 GMC - Fuel Pump 'B' Low Flow/Performance - AutoCodes.com — P2636 GMC Code - Fuel Pump 'B' Low Flow/Performance

What does this mean?

What are the Possible Causes of the DTC P2636 GMC?

Faulty fuel pump relay
Faulty fuel pump
Fuel pump harness is open or shorted
Fuel pump circuit poor electrical connection
Faulty fuel pump control module (if applicable)

How to Fix the DTC P2636 GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

There are factory service bulletins for the following GMC models:

2001 GMC Sierra
2002 GMC Sierra
2003 GMC Sierra
2004 GMC Sierra
2005 GMC Sierra
2001-2005 GMC Sierra Factory Service Bulletin OBDII Code P2636

2007 GMC Sierra 3500 Chassis Cab
2008 GMC Sierra 3500 Chassis Cab
2009 GMC Sierra 3500 Chassis Cab
2007-2009 GMC Sierra 3500 Chassis Cab Factory Service Bulletin ODBII Code P2636

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P2636 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P2636 GMC code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.