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 fuel tank to the right side of fuel tank through the internal fuel transfer tube. The primary fuel level sender and the secondary fuel level sender change resistance to the fuel level. The engine control module (ECM) observes the signal circuit of both fuel level senders in order to determine the fuel level. When the fuel tank is full, both fuel level senders have high resistance, and the ECM senses a high voltage on both signal circuits of the fuel level senders. When the fuel tank is empty, both fuel level senders have low resistance, and the ECM senses a low voltage on both signal circuits of the fuel level senders.

The following table illustrates the difference between temperature, resistance, and voltage:

The ECM detects fuel level sender 1 is greater than the upper threshold and fuel level sender 2 is less than the lower threshold for greater than 120 seconds.

DTC P2636 is a Type C DTC.

DTC P2636 is a Type C DTC.

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, 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.

1. Ignition OFF, and the MAIN fuse removed, disconnect the fuel tank in-line harness connector X304.
2. Test for less than 5 ohms of resistance between the low reference circuit terminal 8 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance, if the circuit tests normal, replace the ECM.

3. Test for less than 5 ohms of resistance between the low reference circuit terminal 3 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance, if the circuit tests normal, replace the ECM.

4. Install the MAIN fuse. Ignition ON, verify both of the scan tool Fuel Level Sensor voltage parameters are at 5 volts.

⇒	If less than the specified range, test the appropriate signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

Important: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage, and the sensor may be damaged.

5. Install a 3A fused jumper wire between the signal circuit terminal 7 and ground. Verify the scan tool Fuel Level Sensor-Left Tank voltage parameter is at 0 volts.

⇒	If greater than the specified range, test the signal circuit for a high resistance. if the circuit tests normal, replace the ECM.

6. Install a 3A fused jumper wire between the signal circuit terminal 2 and ground. Verify the scan tool Fuel Level Sensor-Right Tank voltage parameter is at 0 volts.

⇒	If greater than the specified range, test the signal circuit for a high resistance. if the circuit tests normal, replace the ECM.

7. Remove the fuel tank.
8. 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.

9. If all circuits test normal, test or replace the left/secondary fuel level sensor.

1. Ignition OFF, remove the left fuel level sender from the fuel tank.
2. Test the resistance between terminal A and terminal D of the left fuel level sender. 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 not within the specified range or changes erratically while moving the float arm from stop to stop, replace the fuel level sender.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.