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.

### Circuit/System Description

The fuel level sensor changes resistance in response to the fuel level. The engine control module (ECM) monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the sensor resistance is low and the ECM senses a low signal voltage. When the fuel tank is empty, the sensor resistance is high and the ECM senses a high signal voltage. The ECM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the tank.

The ECM sends the fuel level percentage via serial data circuit to the instrument cluster in order to control the fuel gage. Then fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.

### Reference Information

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

1. Ignition OFF, disconnect CXXX, install a signal generator and instrument panel tester between the signal circuit and the low reference circuit.
2. Ignition ON, vary the resistance on the signal generator from 40-250 ohms and monitor the fuel gage.

⇒ | If the fuel gage displays the correct fuel level, test the signal circuit for an open/high resistance between CXXX and the fuel level sender. If the circuit tests normal, test the low reference circuit for an open/high resistance between CXXX and the fuel level sender.

⇒ | If all circuits test normal, replace the fuel level sender.

3. Ignition ON, vary the resistance on the signal generator from 40-250 ohms. Verify that the scan tool Fuel Tank Level Remaining parameter displays the correct fuel level percent.

⇒ | If the fuel level percent is correct, replace the instrument panel cluster (IPC).

⇒ | If the fuel level percent is incorrect, test the signal circuit for an open/high resistance. If the circuit tests normal, test the low reference circuit for an open/high resistance.

⇒ | If all circuits test normal, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Level Sensor Replacement or Fuel Level Sensor Replacement or Fuel Level Sensor Replacement or Fuel Level Sensor Replacement in Section 1F2, Engine Controls-FAM II 2.4D