For 1990-2009 cars

### 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. If the control module determines that the right side fuel level is less than a predetermined amount of the left side fuel level, this DTC sets.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2636 Fuel Transfer Pump Flow Insufficient

### 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 running.

• | The ECM does not detect sensor signal condition.

• | The fuel level is stable.

• | DTC P2636 runs continuously once the above conditions exist for more than 4 minutes.

### Conditions for Setting the DTC

• | The ECM detects that the right side fuel level (fuel level 1) is lower than 10.6 percent, and the left side fuel level (fuel level 2) is higher than 22.8 percent.

• | The above condition is present for more than 4 seconds.

### Action Taken When the DTC Sets

• | The control module stores the DTC information into memory when the diagnostic runs and fails.

• | The malfunction indicator lamp (MIL) will not illuminate.

• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

• | The ECM commands the fuel gage to empty.

• | The driver information center displays Low Fuel.

### Conditions for Clearing the DTC

• | A current DTC Last Test Failed clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

• | Clear the DTC with the scan tool.

### Conditions for Clearing the DTC

• | A current DTC Last Test Failed clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

• | Clear the DTC with a scan tool.

### Diagnostic Aids

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views .

• | 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. Remove the fuel level sensor. Refer to Primary Fuel Tank Module Replacement in order to test the resistance of the fuel level sensor. The resistance of the fuel level sensor should change between 40-250 ohms. Replace the sensor if the resistance did not change or was out of range.

• | For an intermittent condition, refer to Intermittent Conditions .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step determines if a condition current.

2. This step verifies possible component problems within the fuel tank.

#### P2636

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Start the engine.
2. Allow the engine to idle for the specified amount of time.
3. Observed the DTC Info with a scan tool.

Does the DTC fail this ignition?

5 minutes

Go to Step 4

Go to Step 3

3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn the ignition switch to ON position, with the engine OFF.
2. Raise the vehicle. Refer to Lifting and Jacking the Vehicle .
3. Disconnect the left side fuel level sensor harness connector.
4. Connect a 3-amp fused jumper wire between the signal circuit of the left fuel level sensor and a good ground.
5. Monitor the Fuel Level Sensor Left Tank voltage parameter with a scan tool.

Is the voltage at the specified value?

0.0 V

Go to Step 5

Go to Step 6

5 |

1. Connect a 3-amp fused jumper wire between the signal circuit of the left fuel level sensor and the low reference circuit of the left fuel level sensor.
2. Monitor the Fuel Level Sensor Left Tank voltage parameter with a scan tool.

Is the voltage at the specified value?

0.0 V

Go to Step 8

Go to Step 7

6 | Test the signal circuit of the left fuel level sensor for high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10
7 | Test the low reference circuit of the left fuel level sensor for high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10
8 |

1. Remove the fuel tank. Refer to Fuel Tank Replacement .
2. Remove the fuel tank primary and secondary modules. Refer to Primary Fuel Tank Module Replacement and Secondary Fuel Tank Module Replacement .
3. 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

Did you find and correct the condition?

--

Go to Step 13

Go to Step 9

9 | Test for an intermittent and for a poor connection at the left fuel level sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11
10 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12
11 | Replace the left fuel level sensor. Refer to Secondary Fuel Tank Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | --
12 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | --
13 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 14

14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK