GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 DTC 168

Circuit Description

The fuel level sensor in the fuel tank is a variable resistor. As the fuel level changes, the resistance of the fuel sensor changes. The instrument panel cluster (IPC) monitors changes in the voltage caused by the changes in the resistance of the sensor to determine fuel level.

Conditions for Setting the DTC

The fuel gauge circuit is tested every 100 ms. DTC 168 will set in the following ways:

    • When the circuit is open.
    • Shorted to battery.
    • The resistance of the fuel sensor is out of range (more than 350 ohms) for more than 8 seconds.

Action Taken When the DTC Sets
    • Stores a DTC 168 in memory.
    • The fuel gage will return to the zero position.

Conditions for Clearing the MIL/DTC
    • The resistance must be greater than 350 ohms for 4 seconds to clear the fault in the next monitoring cycle.
    • Conditions for the fault are no longer present.
    • Using a 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 (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.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This test determines whether there is a short to voltage or the open in the fuel level signal circuit or if there is an internal IPC problem.

    2.

  2. This test determines whether the short to voltage or the open is in the fuel level signal circuit or if there is an internal fuel sender problem.

    3.

  3. This test determines whether the short to voltage or the open is in the fuel level signal circuit or if there is an internal ECM problem.

    4.

  4. Clear all DTCs within the IPC after performing this diagnostic table.

Step

Action

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the IPC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

2
  1. Disconnect the instrument cluster connector.
  2. Test the fuel level signal circuit for a short to voltage and an open. Refer to Circuit Testing in Wiring Systems.

Is a short to voltage or an open present?

Go to Step 3

Go to Step 6

3
  1. Disconnect C400.
  2. Test the fuel level signal circuit for a short to voltage and an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is a short to voltage or an open present?

Go to Step 4

Go to Step 7

4
  1. Disconnect the Engine Control Module (ECM).
  2. Test the fuel level signal circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 5

5

Important: Program the replacement ECM.

Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls.

Did you complete the replacement?

Go to Step 8

--

6

Important: Program the replacement IPC.

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

Go to Step 8

--

7

Replace the fuel level sender. Refer to Fuel Sender Assembly Replacement in Engine Controls.

Did you complete the replacement?

Go to Step 8

--

8
  1. Use the scan tool in order to clear the IPC and ECM DTCs.
  2. Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2