GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The fuel level sensor changes resistance based on the fuel level. The PCM monitors the signal circuit of the fuel level sensor in order to determine the fuel level. When the fuel tank is full, the fuel level sensor resistance is high and the PCM senses a high fuel level sensor signal voltage. When the fuel tank is empty, the fuel level sensor resistance is low and the PCM senses a low fuel level sensor signal voltage. The PCM uses the signal circuit of the fuel level sensor in order to calculate the total remaining fuel percent in the tank. The PCM sends the fuel level percentage via the fuel level signal circuit to the instrument panel cluster (IPC) in order to control the fuel gage.

The PCM sets this DTC if the fuel level signal circuit to the IPC becomes open, shorted to voltage, or shorted to ground.

Conditions for Running the DTC

The ignition is ON, with the engine OFF.

Conditions for Setting the DTC

The PCM detects a malfunction in the fuel level signal circuit for more than 5 seconds.

Action Taken When the DTC Sets

The PCM records the operating conditions at the time the diagnostic fails. The PCM stores 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 help determine the number of miles since the DTC set. The Fail Counter and Pass Counter can also help determine the number of ignition cycles that the diagnostic test reported a pass and/or fail. Operate the vehicle within the same freeze frame conditions including those for RPM, for engine load, for vehicle speed, for temperature, and for others. This will isolate at what point the DTC failed.

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

Step

Action

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the Instrument Cluster Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2

Is DTC P1665 a current code?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

  1. Disconnect C2 at the PCM.
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the fuel level signal circuit and a good ground.
  3. Turn the ignition ON, with the engine OFF.
  4. Important:: Verify the J 33431-C Signal Generator and Instrument Panel Tester resistance settings with a DMM.

  5. Vary the resistance on the J 33431-C from 0-90 ohms.

Does the fuel gage move from empty to full?

Go to Step 6

Go to Step 4

4

Test the fuel level signal circuit to the IPC for an open, for a short to voltage, or 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 9

Go to Step 5

5

Inspect for poor connections at the harness connector of the IPC. 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 9

Go to Step 7

6

Inspect for poor connections at the harness connector of the 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 9

Go to Step 8

7

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

Go to Step 9

--

8

Important:: Program the replacement PCM.

Replace the PCM. Refer to the appropriate procedure:

    •  Powertrain Control Module Replacement in Engine Controls - 4.3L
    •  Powertrain Control Module Replacement in Engine Controls - 5.0L and 5.7L
    •  Powertrain Control Module Replacement in Engine Controls - 8.1L

Did you complete the replacement?

Go to Step 9

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9

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

Does the DTC reset?

Go to Step 2

System OK