Diagnostic Aids
Important: The gauge will display the dormant fuel level for 10 seconds when the fuel gauge selector switch is pressed. It will then return to normal operation.
Check for the following conditions:
| • | Verify that the CNG fuel tank is at least one-third full (1,200 psi). Add fuel if needed. |
| • | Verify that no AF Diagnostic Trouble Codes (DTCs) are set. |
| • | Verify that the Fuel Sending Unit (FSU) connector is connected. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Does the fuel gauge read close to empty? | -- | Go to Step 12 | Go to Step 2 |
2 | Was the fuel indicator lamp illuminated? | -- | Go to Step 4 | Go to Step 3 |
3 |
Does the fuel gauge read empty? | -- | Go to Step 8 | Go to Step 6 |
4 |
Does the fuel gauge read empty? | -- | Go to Step 5 | Go to Instrument Cluster Diagnosis in Instrument Panel, Gauges and Console in the 1997 C/K Truck Service Manual |
5 |
Was a problem found? | -- | Go to Step 10 | Go to Step 11 |
6 |
Is there continuity? | -- | Go to Step 7 | Go to Step 10 |
7 | Inspect for a faulty connection at ECU connector C001. Was a problem found? | -- | Go to Step 10 | Go to Step 11 |
8 | Inspect for a poor connection at the FSU connector C315. Was a problem found? | -- | Go to Step 10 | Go to Step 9 |
9 | Replace the FSU. Refer to Fuel Sender Replacement . Is the action complete? | -- | Go to Step 12 | -- |
10 | Repair the circuit as necessary. Refer to Repair Procedures in Electrical Diagnosis in the 1997 C/K Truck Service Manual. Is the action complete? | -- | Go to Step 12 | -- |
11 | Replace the ECU. Refer to Engine Control Unit Replacement . Is the action complete? | -- | Go to Step 12 | -- |
12 |
Does the fuel gauge read normal? | -- | Fuel Gauge OK | Go to Step 1 |
