2001 GMC C3500 Fuel guage or sending unit

Tiny
ROCKETANSKY
  • MEMBER
  • 2001 GMC C3500
  • V8
  • 4WD
  • MANUAL
  • 114,000 MILES
I was off roading my dually pick when all of a sudden my low fuel light came on stating "fuel level low" when I had 3/4 tank. Even after re-filling the tank the fuel guage shows empty/does not work and the message center says "fuel level low." My DTC reader gave me 2 trouble codes P0461 and P0463. P0461 says "fuel level sensor performance" and P0463 says "fuel level sensor circuit high voltage". My diagnosis is the fuel sending unit/float. I cannot find any fuse or relay to those sensors. Can you help. Thanks Sean
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Thursday, October 29th, 2009 AT 10:37 PM

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Tiny
DR LOOT
  • EXPERT
2001 GMC had a recall on the cluster, unfortunately. It was the fuel gauge. On the diesel and a gas. But you can go ahead and diagnose the problem with the following procedures:

DTC P0461Circuit Description The fuel level sensor changes resistance in response to 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 circuit voltage. When the fuel tank is empty, the fuel level sensor resistance is low and the PCM senses a low fuel level sensor signal circuit voltage. The PCM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the fuel 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. This diagnostic table tests for a stuck fuel level sensor. The PCM sets this DTC if the fuel level sensor appears to be stuck, based on a lack of fuel level sensor signal variation expected during normal operation.

Conditions for Running the DTC The ignition is ON. Conditions for Setting the DTC The PCM does not detect a change in fuel level of at least 3.0 L (0.79 gal) over a distance of 322 km (200 mi). Action Taken When the DTC Sets The fuel gage defaults to empty. 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 in determining 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 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 when the DTC failed. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS.

DTC P0463Circuit Description The fuel level sensor changes resistance in response to 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 circuit voltage. When the fuel tank is empty, the fuel level sensor resistance is low and the PCM senses a low fuel level sensor signal circuit voltage. The PCM uses the signal circuit of the fuel level sensor in order to calculate the percentage of remaining fuel in the fuel 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. Conditions for Running the DTC The ignition is ON. Conditions for Setting the DTC The fuel level signal is greater than 98%. The above condition is present for greater than 20 seconds. Action Taken When the DTC Sets The fuel gage defaults to empty. 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 help in determining 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 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 when the DTC failed. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS. Test Description The number below refers to the step number on the diagnostic table.3. Tests for the proper operation of the circuit in the low voltage range.

If you need anything else, let me know.
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Tuesday, November 3rd, 2009 AT 7:44 PM

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