Fuel Gage Inaccurate or Inoperative Dual Tanks
Diagnostic Instructions
Perform the Diagnostic System Check - Instrument Cluster 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
| • | Engine Controls Schematics for the 4.8L, 5.3L, 6.0L engine |
| • | Engine Controls Schematics for the 8.1L engine |
Connector End View Reference
| • | 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
| • | Fuel System Description for the 4.8L, 5.3L, 6.0L engine |
| • | Fuel System Description for the 8.1L engine |
Electrical Information Reference
Scan Tool Reference
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
All Engines Except 5.3L
- Ignition OFF, disconnect the harness connectors at the primary and secondary fuel level sensors.
- Ignition OFF, test for less than 1.0 ohm of resistance between the primary fuel level sensor low reference circuit and ground.
- Ignition OFF, test for less than 1.0 ohm of resistance between the secondary fuel level sensor low reference circuit and ground.
- 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.
- 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.
- 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.
- If all circuits test normal, perform the fuel level sensor component test before replacing either the primary or secondary fuel level sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM. |
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM. |
| ⇒ | If not displaying the specified range, test both signal circuits for an open/high resistance. If the circuits test normal, replace the PCM. |
| ⇒ | If not displaying the specified range, replace the IPC. |
5.3L Engine Only
- Ignition OFF, disconnect the harness connectors at the primary and secondary fuel level sensors.
- Ignition OFF, test for less than 1.0 ohm of resistance between the primary fuel level sensor low reference circuit and ground.
- Ignition OFF, test for less than 1.0 ohm of resistance between the secondary fuel level sensor low reference circuit and ground.
- 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.
- 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 33 and 67 percent as the signal generator resistance changes.
- Vary the signal generator resistance between 20 and 125 ohms. Verify that the fuel gage displays a range that varies between one third full and two thirds full as the signal generator resistance changes.
- If all circuits test normal, perform the fuel level sensor component test before replacing either the primary or secondary fuel level sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM. |
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM. |
| ⇒ | If not displaying the specified range, test both signal circuits for an open/high resistance. If the circuits test normal, replace the PCM. |
| ⇒ | If not displaying the specified range, replace the IPC. |
Component Testing
- Ignition OFF, disconnect the harness connectors at the primary and secondary fuel level sensors.
- 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.
- 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.
| ⇒ | If not within the specified range, replace the primary fuel level sensor. |
| ⇒ | If not within the specified range, replace the secondary fuel level sensor. |
Repair Instructions
| • | Powertrain Control Module Replacement for the 4.8L, 5.3L, 6.0L engine |
| • | Powertrain Control Module Replacement for the 8.1L engine |
| • | Fuel Level Sensor Replacement for the 4.8L, 5.3L, 6.0L engine |
| • | Fuel Level Sensor Replacement for the 8.1L engine |
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 PCM Enhanced Evap Data list. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for high resistance in the signal circuit and the low reference circuit of the fuel level sender.
-
DTCs will be set in the PCM when you perform this diagnostic table.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | ||||||||||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |||||||||
2 |
Important: Verify the J 33431-C resistance settings with a DMM. Does the fuel gage display the correct fuel level? | -- | Go to Step 4 | Go to Step 3 | ||||||||
Important: Verify the J 33431-C resistance settings with a DMM. Important: Turn OFF the ignition momentarily between the resistance settings in order to quickly update the scan tool display. Does the scan tool display the correct fuel level percent? | -- | Go to Step 11 | Go to Step 5 | |||||||||
4 | Inspect for the following items:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 7 | ||||||||
5 | Test the signal circuit of the fuel level sender for a high resistance between C152 and the powertrain control module (PCM). Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 6 | ||||||||
6 | 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 13 | Go to Step 9 | ||||||||
7 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 8 | ||||||||
8 |
Does the resistance change smoothly across the specified range? | 40-250 ohms | Go to Diagnostic Aids | Go to Step 10 | ||||||||
9 | 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 13 | Go to Step 12 | ||||||||
10 | Replace the fuel level sender. Refer to the following procedures:
Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||
11 | Replace the instrument panel cluster (IPC). Refer to Instrument Cluster Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||
12 |
Important: Program the replacement PCM. Replace the PCM. Refer to:
Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||
Did you correct the condition? | -- | System OK | Go to Step 2 | |||||||||
