For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P2636 58: Fuel Transfer Pump Flow Insufficient Incorrect reaction After Event

### 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 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:

Fuel Level-Right or Left Sensor | Fuel Level Sensor Resistance | Fuel Level Sensor Voltage
--- | --- | ---
Empty | Low | Low
Full | High | High

### Conditions for Running the DTC

• | The ignition is ON.

• | The DTC runs continuously when the above condition is met.

### Conditions for Setting the DTC

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

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

Engine idling , observe the DTC information parameter with a scan tool. DTC P2636 should not set.

### Circuit/System Testing

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/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. 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 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 after completing the diagnostic procedure.

• | Fuel Tank Draining

• | Fuel Tank Replacement

• | Primary Fuel Tank Module Replacement

• | Secondary Fuel Tank Module Replacement

• | Fuel System Priming

• | Control Module References for engine control module replacement, setup, and programming.