Fuel Gage Inaccurate or Inoperative Vehicle Runs Out at Half Tank
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Does the fuel pump run? | -- | Go to Step 3 | Go to Step 2 |
2 | Replace the fuel transfer pump assembly. Is the repair complete? | -- | System OK | -- |
3 | Connect a J 39200 DMM between the fuel transfer pump harness connector terminal A, and chassis ground. Does the DMM indicate continuity? | -- | Go to Step 5 | Go to Step 4 |
4 | Locate and repair the open in CKT 350 (BLK) between the fuel transfer pump harness connector and G 408. Is the repair complete? | -- | System OK | -- |
5 |
Did the DMM indicate continuity? | -- | Go to Step 7 | Go to Step 6 |
6 | Locate and repair CKT 120 (GRY) between the fuel transfer pump, and the fuel transfer pump relay. Is the repair complete? | -- | System OK | -- |
7 |
Did the test lamp light? | -- | Go to Step 9 | Go to Step 8 |
8 | Locate and repair the open in CKT 145, CKT 139 (PNK) between the IP fuse block and the fuel transfer pump relay. Is the repair complete? | -- | System OK | -- |
9 |
Did the test lamp light? | -- | Go to Step 11 | Go to Step 10 |
10 | Locate and repair the open in CKT 139 (PNK) between S417 and the fuel transfer pump relay. Is the repair complete? | -- | System OK | -- |
11 |
Does the DMM indicate continuity? | -- | Go to Step 13 | Go to Step 12 |
12 | Locate and repair the open in CKT 497 (LT GRN) between the fuel sender and balance pump control module and the fuel transfer pump relay. Is the repair complete? | -- | System OK | -- |
13 |
Did the test lamp light? | -- | Go to Step 15 | Go to Step 14 |
14 | Replace the fuel transfer pump relay. Is the repair complete? | -- | System OK | -- |
15 | Connect a test lamp between the fuel sender and balance pump control module connector terminal A and chassis ground. Did the test lamp light? | -- | Go to Step 17 | Go to Step 16 |
16 | Locate and repair the open in CKT 139 (PNK) between S417 and the fuel sender and balance pump control module. Is the repair complete? | -- | System OK | -- |
17 | Connect a J 39200 between the fuel sender and balance pump control module connector terminal E and chassis ground. Does the DMM indicate continuity? | -- | Go to Step 18 | Go to Step 19 |
18 | Replace the fuel sender and balance pump control module. Is the repair complete? | -- | System OK | -- |
19 | Locate and repair the open in CKT 350 (BLK) between S415 and the fuel sender and balance pump control module. Is the repair complete? | -- | System OK | -- |
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 . |
| • | Use the fuel sender resistance (0-90 ohms) to verify the fuel level sender operation. When the fuel tank is empty the sender resistance is 0 ohms and when the fuel tank is full the sender resistance is 90 ohms. |
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Verify the J 33431-C resistance settings with a DMM. Does the fuel gauge display the correct fuel level? | -- | Go to Step 2 | Go to Step 3 | ||||||
2 | Inspect for the following items:
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 5 | ||||||
3 | Test the signal circuit of the fuel level sender for an open, a short to ground or a high resistance between the fuel level sender and the IPC. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 4 | ||||||
4 | Test the fuel sender ground circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 | ||||||
5 |
Did you find and correct the condition? | Go to Step 10 | Go to Step 6 | |||||||
6 |
Does the resistance change smoothly across the specified range? | 0-90 ohms | Go to Diagnostic Aids | Go to Step 8 | ||||||
7 | 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 10 | Go to Step 9 | ||||||
8 | Replace the fuel level sender. Refer to Duramax® Medium Duty Diesel Engine Manual - 7.8 L. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
10 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 1 |
Fuel Gage Inaccurate or Inoperative Dual 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 . |
| • | Use the fuel sender resistance (0-90 ohms) to verify the fuel sender operation. When the fuel tank is empty, the sender resistance is 0 ohm and when the fuel tank is full the sender resistance is 90 ohms. |
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Verify the J 33431-C resistance settings with a DMM. Does the fuel gauge display the correct fuel level? | -- | Go to Step 3 | Go to Step 2 | ||||||
2 |
Important: Verify the J 33431-C resistance settings with a DMM. Does the fuel gauge display the correct fuel level? | -- | Go to Step 5 | Go to Step 4 | ||||||
3 | Inspect for the following items:
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 8 | ||||||
4 | Test the fuel level sensor signal circuit for an open, a short to ground or a high resistance between the IPC and the balance pump control module. 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 | ||||||
5 | Test the signal circuits of the fuel level senders for an open, a short to ground or a high resistance between the fuel level senders and the balance pump control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 6 | ||||||
6 | Test the ground circuit of the fuel level senders for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 10 | ||||||
7 | Test the ground circuit of the balance pump control module for an open or a high resistance. 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 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 9 | ||||||
9 |
Does the resistance change smoothly across the specified range? | 0-90 ohms | Go to Diagnostic Aids | Go to Step 12 | ||||||
10 | Inspect for poor connections at the harness connector of the balance pump control module. 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 | ||||||
11 | 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 | ||||||
12 | Replace the primary or the secondary fuel level sender. Refer to Duramax® Medium Duty Diesel Engine Manual - 7.8 L. Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
13 | Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
14 | Replace the balance pump control module. Refer to Duramax® Medium Duty Diesel Engine Manual - 7.8 L. Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
15 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 1 |
