P2636 CHEVROLET - Fuel Pump 'B' Low Flow/Performance

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3  What does this mean?

Possible causes

  • 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)

Tech notes

There are factory service bulletins for the following Chevrolet Models:

2001-2005 Chevrolet Silverado
2001-2005 Chevrolet Silverado Factory Service Bulletin OBDII Code P2636

2007-2009 Chevrolet Silverado 3500 Chassis Cab
2007-2009 Chevrolet Silverado 3500 Chassis Cab Factory Service Bulletin ODBII Code P2066 And/Or P2636

Models: 2007-2008 Chevrolet Corvette
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Some customers may comment that the Fuel gauge goes to empty when the fuel level is greater than what is shown on the gauge and DTCs P2066 and P2636 are present. When these codes are present the Fuel Level Low message should be displayed on the DIC. This could be caused if the ECM does not receive the expected voltage signal to indicate that the fuel transfer is properly occurring. If this condition exists for 30 minutes both of these DTCs will be set. The fuel level sensor card may have slight discoloration possibly caused by fuel contamination which can affect the level sensor output. The fuel level sensor diagnostics are sensitive to this issue.

Verify that P2066 and P2636 DTC are set.
Confirm fuel rail pressure with the fuel pump on is 58-62 psi. If the pressure is not within this range, follow eSI Service Procedures.
Confirm proper jet pump transfer by checking and recording the fuel level sensor voltages using a Tech2. This must be performed with less than 3/4 tank of fuel. If required, remove sufficient fuel from the Schrader valve on the fuel rail. Follow all safety procedures as outlined in SI. Clear the DTCs to get a reading on the fuel gage. If the secondary (passenger side) sender is less than 2.2 volts and the primary (driver side) is more than .86 volts, the secondary (passenger side) level sensor and the module (includes the jet pump) should be replaced. Prior to replacing fuel hardware confirm all wiring connections are fully seated and harnesses are properly routed.
If the jet transfer pump is operating properly the fuel sender card may be contaminated. This could cause an incorrect voltage signal to be sent to the ECM. Customers should be advised to correct a contamination issue by adding one bottle of GM Fuel System Treatment PLUS (part number 88861011) to the fuel system on their next fuel fill. Note; the fuel level must be below ΒΌ tank when the fuel treatment is added. The treatment rate is 1 oz. per gallon of fuel (Using one 20 oz bottle to the fuel system is acceptable). To clean a severely contaminated fuel level sensor, it is permissible to treat the fuel system on two consecutive tanks.
Note: Back to back treatment is only permitted once in the life of the vehicle. After the initial treatment, customers should be advised to add one bottle of GM Fuel System Treatment PLUS to the fuel tank at every oil change, however, not more frequently than once every 3000 miles.

User Submitted Video

Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P2636 Chevrolet 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 Chevrolet - Fuel Pump 'B' Low Flow/Performance - Engine-Codes.com
Repair Importance Level: 3
1=Low 2=Medium 3=High  
Repair Difficulty Level: 3
1=Easy 2=Moderate 3=Hard  
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