GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 Yukon Denali 🢒 Body 🢒 Instrument Panel, Gages, and Console 🢒 Fuel Gage Inaccurate or Inoperative

Fuel Gage Inaccurate or Inoperative Dual Tanks

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Fuel Level Sensor Signal - Primary

P0462

P0463

P0463

P0461, P0464

Fuel Level Sensor Signal - Secondary

P0462

P0463

P0463

P0461, P0464

Low Reference

--

P0463

P0463

P0461, P0464

Circuit/System Description

The fuel level sensor changes resistance in response to the fuel level. The powertrain control module (PCM) monitors the signal circuits of the primary and secondary fuel level sensors in order to determine the fuel level. The PCM uses the signal circuits of the primary and secondary fuel level sensors in order to calculate the percentage of remaining fuel in the tanks. The PCM sends the fuel level percentage via serial data to the instrument panel cluster (IPC) in order to display the fuel level on the fuel gage.

Reference Information

Schematic Reference

    •  Instrument Cluster Schematics
    •  Engine Controls Schematics for the 4.8L, 5.3L, 6.0L engine
    •  Engine Controls Schematics for the 8.1L engine

Connector End View Reference

    •  Instrument Panel, Gages, and Console Connector End Views
    •  Powertrain Control Module Connector End Views for the 4.8L, 5.3L, 6.0L engine
    •  Powertrain Control Module Connector End Views for the 8.1L engine

Description and Operation

    •  Instrument Cluster Description and Operation
    •  Fuel System Description for the 4.8L, 5.3L, 6.0L engine
    •  Fuel System Description for the 8.1L engine

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Ignition ON, verify DTC P0461, P0462, P0463, or P0464 is not set.

⇒If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connectors at the primary and secondary fuel level sensors.
  2. Ignition OFF, test for less than 1.0 ohm of resistance between the primary fuel level sensor low reference circuit and ground.
    3. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
  3. Ignition OFF, test for less than 1.0 ohm of resistance between the secondary fuel level sensor low reference circuit and ground.
    4. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
  4. Jumper the primary fuel level sensor signal circuit to the secondary fuel level sensor signal circuit. Install a Signal Generator and Instrument Panel Tester between the jumped signal circuits and ground.
  5. Ignition ON, vary the signal generator resistance between 20 and 125 ohms. Verify that the scan tool Fuel Tank Level Remaining parameter displays a range that varies between 5 and 95 percent as the signal generator resistance changes.
    6. ⇒If not displaying the specified range, test both signal circuits for an open/high resistance. If the circuits test normal, replace the PCM.
  6. Vary the signal generator resistance between 20 and 125 ohms. Verify that the fuel gage displays a range that varies between empty and full as the signal generator resistance changes.
    7. ⇒If not displaying the specified range, replace the IPC.
  7. If all circuits test normal, perform the fuel level sensor component test before replacing either the primary or secondary fuel level sensor.

Component Testing
  1. Ignition OFF, disconnect the harness connectors at the primary and secondary fuel level sensors.
  2. While sweeping the primary fuel level sensor through its full range of motion, test for a minimum value less than 41 ohms and a maximum value greater than 119 ohms of resistance between the signal terminal A and the low reference terminal D.
    3. ⇒If not within the specified range, replace the primary fuel level sensor.
  3. While sweeping the secondary fuel level sensor through its full range of motion, test for a minimum value less than 41 ohms and a maximum value greater than 119 ohms of resistance between the signal terminal A and the low reference circuit terminal D.
    4. ⇒If not within the specified range, replace the secondary fuel level sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for PCM and IPC replacement, setup, and programming

Fuel Gage Inaccurate or Inoperative Single Tank

Diagnostic Aids
    • Ensure that the fuel level is in the same range as the customer concern.
    • For intermittent diagnosis, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • Refer to Fuel Level Specifications in order to verify the correct fuel level sender readings. The fuel level is available on the scan tool in the Fuel Tank Level Remaining (%) parameter in the powertrain control module (PCM) Enhanced evaporative emission (EVAP) Data list.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for high resistance in the signal circuit and the low reference circuit of the fuel level sender.

    2.

  2. DTCs will be set in the PCM when you perform this diagnostic table.

Step

Action

Values

Yes

No

Schematic Reference: Instrument Cluster Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Disconnect C152.
  2. Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the fuel level sender and the low reference circuit of the fuel level sender (male terminal side).
  3. Turn ON the ignition, with the engine OFF.
  4. Vary the resistance on the J 33431-C from 40-250 ohms.

    5. Important: Verify the J 33431-C resistance settings with a DMM.

  5. Refer to Fuel Level Specifications in order to convert from resistance to fuel gage display.

Does the fuel gage display the correct fuel level?

--

Go to Step 5

Go to Step 3

3

  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Vary the resistance on the J 33431-C from 40-250 ohms.

    4. Important: Verify the J 33431-C resistance settings with a DMM.

  4. Refer to Fuel Level Specifications in order to convert from resistance to fuel level percent.

    5. Important: Turn OFF the ignition momentarily between the resistance settings in order to quickly update the scan tool display.

  5. With the scan tool, observe the Fuel Tank Level Remaining % parameter in the powertrain control module (PCM) Enhanced evaporative emission (EVAP) Data list.

Does the scan tool display the correct fuel level percent?

--

Go to Step 4

Go to Step 6

4

With the scan tool, perform the Displays Test in the instrument panel cluster (IPC) scan tool Output Controls.

Does the gage move from 0 to its maximum value and back to 0 when you perform the Displays Test?

--

Go to Step 5

Go to Step 10

5

Inspect for the following items:

    • A poor connection at the harness connector of the fuel level sender--Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
    • A high resistance in the signal circuit or the low reference circuit between the fuel level sender and C152
    • A misaligned fuel level sender
    • A deformed fuel tank

Did you find and correct the condition?

--

Go to Step 15

Go to Step 8

6

Test the signal circuit of the fuel level sender for a high resistance between C152 and the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 7

7

Test the low reference circuit of the fuel level sender for a high resistance between C152 and the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

8
  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 15

Go to Step 9

9
  1. With the DMM, measure the resistance of the fuel level sender while moving the float arm.
  2. Observe both the analog and digital displays on the DMM.

Does the resistance change smoothly across the specified range?

40-250 ohms

Go to Diagnostic Aids

Go to Step 12

10

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

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

11

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

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

12

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 15

--

13

Replace the instrument panel cluster (IPC). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

14

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 15

--

15

  1. Use the scan tool in order to clear the PCM DTCs.
  2. Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2