Diagnostic Test
- CHECK FOR AN ACTIVE DTC
- With the scan tool, read Body Control Module (BCM) DTCs and record on the repair order.
- Record the Environmental Data and any DTCs.
- With the scan tool, erase DTCs.
- Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
- With the scan tool, read BCM DTCs.
Did the DTC return?
Yes
- Go To 3
No
- Go To 2
- MONITOR THE FUEL LEVEL SENSOR VOLTAGE READING FOR AN OPEN SPOT ON THE SENSOR WARNING:
The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in possible serious or fatal injury.
- Disconnect the fuel supply line at the fuel rail.
- Connect a drain hose between the fuel supply line and an approved fuel container.
- Operate the fuel pump to drain the fuel tank until empty.NOTE:
When the Fuel Tank is completely empty, the Fuel Level Sensor should read at or near empty (indicated by a voltage reading of approximately 4.3-4.5 volts) on the scan tool. If the Fuel Tank is near full, the scan tool should read approximately 0.6 volts on the scan tool.
NOTE:Make sure that you have enough fuel to put back into the vehicle to make a good determination of the Fuel Level Sensor voltage feedback. It may be necessary to add more fuel to what was removed in order to do so.
- While monitoring the Fuel Level Sensor voltage reading on scan tool, begin putting fuel back into the Fuel Tank.NOTE:
The Fuel Level Sensor voltage should decrease as fuel is added at a steady rate. Watch for the voltage to change suddenly while fuel is being added. If the voltage suddenly changes to or near 5.0 volts, it would indicate a bad spot (open) on that portion of the sensor.
Did the Fuel Level Sensor reading suddenly change to 5.0 volts at any time while adding fuel?
Yes
- Replace the Fuel Level Sensor in accordance with the Service Information. Refer to SENDING UNIT AND SENSOR, FUEL LEVEL, REMOVAL AND INSTALLATION .
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
- CHECK THE (N4) FUEL LEVEL SIGNAL CIRCUIT VOLTAGE NOTE:
Do not disconnect the Fuel Pump Assembly harness connector during this step. The sensor is powered by a voltage close to the vehicle Battery (minus a diode voltage drop). If disconnected, the voltage reading on the Fuel Level Sensor Signal circuit will be equal to source voltage which is approximately Battery voltage.
- CHECK THE (N4) FUEL LEVEL SENSOR SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
- Turn the ignition off.
- Disconnect the Fuel Pump Assembly harness connector.
- Disconnect the BCM harness connector.
- Measure the resistance of the (N4) Fuel Level Sensor Signal circuit between the Fuel Pump Assembly harness connector and the BCM harness connector.
Is the resistance below 3.0 Ohms?
Yes
- Go To 8
No
- Repair the (N4) Fuel Level Sensor Signal circuit for an open circuit.
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
- CHECK THE VOLTAGE AT THE (G109) FUEL LEVEL SENSE RETURN CIRCUIT NOTE:
Leave the Fuel Pump Assembly harness connector plugged in during this step also.
- CHECK THE (N4) FUEL LEVEL SENSOR SIGNAL CIRCUIT FOR A SHORT TO ANOTHER VOLTAGE SUPPLY
- Turn the ignition off.
- Disconnect the Fuel Pump Assembly harness connector.
- Disconnect the BCM harness connector.
- Check for continuity between the (N4) Fuel Level Sensor Signal circuit and all other circuits at the BCM harness connector.
Is there continuity between the (N4) Fuel Level Sensor Signal circuit and any other circuit?
Yes
- Repair the (N4) Fuel Level Sensor Signal circuit for a short to the circuit that showed continuity.
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
No
- Replace the Fuel Level Sensor in accordance with the Service Information. Refer to SENDING UNIT AND SENSOR, FUEL LEVEL, REMOVAL AND INSTALLATION .
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
- CHECK THE (G109) FUEL LEVEL SENSE RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE
- Measure the resistance of the (G109) Fuel Level Sense Return circuit between the Fuel Pump Assembly harness connector and the BCM harness connector.
Is the resistance below 3.0 Ohms?
Yes
- Go To 8
No
- Repair the (G109) Fuel Level Sense Return circuit for an open or high resistance.
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
- Measure the resistance of the (G109) Fuel Level Sense Return circuit between the Fuel Pump Assembly harness connector and the BCM harness connector.
- CHECK RELATED BCM HARNESS CONNECTIONS
- Disconnect all BCM harness connectors.
- Disconnect all related in-line harness connections (if equipped).
- Disconnect the related component harness connectors.
- Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
- Proper connector installation.
- Damaged connector locks.
- Corrosion.
- Other signs of water intrusion.
- Weather seal damage (if equipped).
- Bent terminals.
- Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
- Terminals that have been pushed back into the connector cavity.
- Perform a terminal drag test on each connector terminal to verify proper terminal tension.
Repair any conditions that are found.
- Reconnect all BCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
- Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
- Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
- With the scan tool, erase DTCs.
- Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
- With the scan tool, read BCM DTCs.
Did the DTC return?
Yes
- Replace the Body Control Module (BCM) in accordance with the Service Information. Refer to MODULE, BODY CONTROL (BCM), REMOVAL AND INSTALLATION .
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
No
- Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
- Test complete.