GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The fuel level sender changes resistance based on the fuel level. The powertrain control module (PCM) monitors the signal circuit of the fuel level sender in order to determine fuel level. When the fuel tank is full, the sender resistance is high and the PCM senses a high signal voltage. When the fuel tank is empty, the sender resistance is low and the PCM senses a low signal voltage. The PCM uses the signal circuit of the fuel level sender in order to calculate the total remaining fuel percent in the tank. The PCM sends the fuel level percent via the class 2 serial data circuit to the body control module (BCM). The IPC receives a class 2 message from the BCM in order to display the fuel level percent on the fuel gage. The fuel level information is also used for misfire and evaporative emission (EVAP) diagnostics.

This diagnostic tests for a lower than normal fuel level sender signal.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0462 Fuel Level Sensor Circuit Low Voltage

Conditions for Running the DTC

The ignition is ON, with the engine ON.

Conditions for Setting the DTC

    • The fuel level signal is less than 3.5%.
    • The above condition is present for greater than 25 seconds.

Action Taken When the DTC Sets

    • The fuel gage defaults to empty.
    • The CHECK GAGES indicator illuminates.
    • The Fuel Level Sensor parameter in the scan tool defaults to 0%.
    • The PCM records the operating conditions at the time the diagnostic fails. The PCM 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 PCM receives the clear code command from the scan tool.

Diagnostic Aids

Use the Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data may aid in determining the number of miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining the number of ignition cycles that the diagnostic reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions, i.e. RPM, engine load, vehicle speed, temperature, etc. This will isolate when the DTC failed.

Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Step

Action

Value(s)

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Disconnect C313.
  2. Connect a test lamp between the fuel level sensor signal circuit on the male terminal side and battery voltage.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 3

3

Connect a test lamp between the fuel level sensor signal circuit on the female terminal side and battery voltage.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 7

4

Test the signal circuit of the fuel level sender for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 7

5

Test the signal circuit of the fuel level sender for a short to ground between C313 and the fuel level sender. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 6

6

Inspect for poor connections at the harness connector of the fuel level sender. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

7

Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 9

8

Replace the fuel level sender. Refer to Fuel Level Sensor Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 10

--

9

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 10

--

10

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK