Diagnostic Aids

• If DTCs P0110, P0115, and P0120 are also set, the malfunction may be in the sensor ground circuit.
• If a DTC P0120 is also set, the malfunction may be in the reference voltage circuit.
• If a DTC P0450 is intermittent, road test the vehicle while observing the fuel tank pressure sensor with a scan tool. A momentary reading of -30.0 mm Hg (-16 in H2O) or less may indicate an intermittent short to ground in the sensor input circuit. A momentary reading of 15.0 mm Hg (8 in H2O) or more may indicate an open in the sensor input or ground circuit.
• If a DTC P0450 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure .
• The EVAP system diagnostic can be monitored on the scan tool under the I/M System Information selection. When the EVAP test displays a YES status, indicating that the system diagnostic is completed, check for DTC P0450 in the Last Test Failed screen of the scan tool. If there is no DTC P0450 displayed the EVAP system diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that the I/M System Information tests only indicate that the test has run, not if the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .

Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.