GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Chevy Suburban - 4WD 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 DTC P2066

Circuit Description

The primary fuel level sender and the secondary fuel level sender changes resistance based on fuel level. The PCM monitors the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to determine the fuel level. When the fuel tank is full, the resistance of both fuel level senders are high and the PCM senses a high signal voltage on both the signal circuits of the primary fuel level sender and the secondary fuel level sender. When the fuel tanks are empty, the resistance of the fuel level senders are low and the PCM senses a low signal voltage. The PCM uses the signal circuits of the primary fuel level sender and the secondary fuel level sender in order to calculate the percentage of remaining fuel in the tank. The PCM sends the fuel level percentage via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and EVAP diagnostics.

This diagnostic tests for a stuck secondary fuel level sender signal. The PCM sets this DTC if the secondary fuel level sender signal appears to be stuck based on a lack of signal variation expected during normal operation.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The PCM does not detect a change in the secondary fuel level of at least 3.0 L (0.79 gal) over a distance of 320 km (200 mi).

Action Taken When the DTC Sets
    • The fuel gage defaults to empty.
    • The low fuel indicator illuminates.
    • 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 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.

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
  1. Remove the fuel level sender.
  2. Inspect for the following items:
    3. • A stuck fuel level sender, i.e. the fuel strainer interfering with the sender float arm
    • Foreign material in the fuel tank, i.e. ice

Did you find and correct the condition?

Go to Step 4

Go to Step 3

3

Replace the fuel level sender. Refer to the following procedures:

    •  Fuel Level Sensor Replacement in Engine Controls - 4.8L, 5.3L and 6.0L
    •  Fuel Level Sensor Replacement in Engine Controls - 8.1L

Did you complete the replacement?

Go to Step 4

--

4
  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