P2636
DTC P2636
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptor
DTC P2636
- Fuel Transfer Pump Flow Insufficient
Circuit Description
The fuel tank on this vehicle is equipped with 2 fuel level sensors, one for each reservoir of the fuel tank. Fuel is transferred from the left side of the fuel tank to the right side of the fuel tank in order to ensure all of the usable fuel volume is available. The fuel pump supplies a small amount of pressurized fuel to the siphon jet pump through the fuel feed pipe. The pressurized fuel creates a venturi action inside the siphon jet pump. The venturi action causes the fuel to be drawn out of the left side of the fuel tank. Fuel is then transferred from the left side of fuel tank to the right side of fuel tank through the internal fuel transfer tube. This diagnostic tests for too large of a difference in fuel level between the left and right side of the fuel tank. The DTC sets if the control module determines that the right side fuel level is less than a predetermined amount of the left side fuel level.
The following table illustrates the difference between temperature, resistance, and voltage:
Conditions for Running the DTC
* Before the engine control module (ECM) can report DTC P2636 failed, DTCs P0462, P0463, P2067, and P2068 must run and pass.
* The engine is operating.
* DTC P2636 runs continuously once the above conditions exist for greater than 4 minutes.
Conditions for Setting the DTC
* The ECM detects that the right side fuel level is less than 11 percent and the left side fuel level is greater than 23 percent.
* The above condition is present for greater than 4 seconds or for a cumulative of 50 seconds.
Action Taken When the DTC Sets
DTC P2636 is a Type C DTC.
Conditions for Clearing the MIL/DTC
DTC P2636 is a Type C DTC.
Diagnostic Aids
Depending on the current fuel level, it may be difficult to locate a malfunctioning fuel level sensor. The condition may only occur when the fuel level is full or near empty. The fuel level sensor unit may need to be removed for further diagnosis. A fuel level sensor that has an intermittent condition causes this DTC to set.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Fuel System Description (Fuel System Description)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Engine idling for 5 minutes, observe the DTC information with a scan tool. DTC P2636 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector of the left side fuel level sensor.
2. Ignition ON, verify the scan tool Fuel Level Sensor-Left Tank voltage parameter is at 5.0 volts.
• If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
3. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Fuel Level Sensor-Left Tank voltage parameter is at 0.0 volts.
• If greater than the specified value, test the signal circuit for a high resistance. If the circuit tests normal, replace the ECM.
4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal D. Verify the scan tool Fuel Level Sensor-Left Tank voltage parameter is at 0.0 volts.
• If greater than the specified value, test the low reference circuit for a high resistance. If the circuit tests normal, replace the ECM.
5. Remove the fuel tank.
6. Remove the fuel tank primary and secondary modules and inspect for the following conditions:
* A clogged secondary fuel strainer and pick up
* A clogged or restricted siphon jet pump
* Broken, clogged or restricted flex tubes, primary fuel tank module
* Broken, clogged, disconnected, or restricted fuel transfer tube inside tank
• If you find any of the above conditions, repair as necessary.
7. If all circuits/connections test normal, test or replace the left/secondary fuel level sensor.
Component Testing
1. Ignition OFF, remove the left fuel level sender from the fuel tank.
2. Connect a DMM between terminal A and terminal D.
3. Verify the secondary fuel level sender resistance remains within 40-250 ohms and changes smoothly while moving the float arm from stop to stop.
• If the resistance is outside the specified range or changes erratically while moving the float arm from stop to stop, replace the fuel level sender.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fuel Tank Draining (Service and Repair)
* Fuel Tank Replacement (Service and Repair)
* Primary Fuel Tank Module Replacement (Primary Fuel Tank Module Replacement)
* Secondary Fuel Tank Module Replacement (Secondary Fuel Tank Module Replacement)
* Fuel System Cleaning (Service and Repair)
* Control Module References (Programming and Relearning) for engine control module replacement, setup, and programming