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 P0462: Fuel Level Sensor 1 Low Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Fuel Level Sensor Reference Voltage Circuit | P0462 | -- | -- | P0461
Fuel Level Sensor Signal Circuit | P0462 | P0463 1 P0464 | P0463 | P0461
Fuel Level Sensor Low Reference Circuit | -- | P0463 1 P0464 | P0463 | P0461
1. Fuel Gage Inaccurate or Inoperative

### 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 GMLAN serial data circuit to the instrument cluster in order to control the fuel gage. The fuel information is also used for misfire and evaporative emission (EVAP) diagnostics.

### Conditions for Running the DTC

• | The ignition is ON, with the engine running.

• | The system voltage is between 9-16 volts.

### Conditions for Setting the DTC

• | The sender output is less than 0.5 volt.

• | The above condition is present for greater than 30 seconds.

### Action Taken When the DTC Sets

• | The fuel gage defaults to empty.

• | The low fuel indicator illuminates.

• | The ECM records the operating conditions at the time that the diagnostic test fails. The ECM displays the failure information in the Failure Records on the scan tool.

### Conditions for Clearing the DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction-free warm-up cycles.

• | The ECM receives a clear code command from the scan tool.

### Circuit/System Verification

Ignition ON, observe the scan tool Fuel Tank Level Remaining parameter. The reading should be between 4 percent and 98 percent.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel level sensor.
2. Ignition ON, verify that the scan tool Fuel Tank Level Remaining parameter is less than 4 percent.

⇒ | If greater than 4 percent, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

3. If all circuits test normal, test or replace the fuel level sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Control Module Replacement for the 2.0L diesel engine.

• | Engine Control Module Replacement for the 2.4L engine.

• | Engine Control Module Replacement for the 3.2L engine.

• | Control Module References for the ECM replacement, setup, and programming