Diagnostic Aids

• If DTCs P0110, P0115, and P0120 are also set, malfunction may be in sensor ground circuit.
• If a DTC P0120 is also set, malfunction may be in reference voltage circuit.
• If a DTC P0450 is intermittent, road test vehicle while observing FTP sensor with a scan tool. A momentary reading of -16 in. H2O or less may indicate an intermittent short to ground in sensor input circuit. A momentary reading of 8 in. H2O or more may indicate an open in sensor input or ground circuit.
• If a DTC P0450 is intermittent, driving vehicle under conditions outlined in Inspection/Maintenance section can verify whether the fault is present. See INSPECTION/MAINTENANCE EVAP SYSTEM SET PROCEDURE  under INSPECTION/MAINTENANCE PROCEDURES (DRIVE CYCLES).
• EVAP system diagnostic can be monitored on scan tool under I/M SYSTEM INFORMATION selection. When EVAP test displays a YES status, indicating system diagnostic is completed, check for DTC P0450 in LAST TEST FAILED screen of scan tool. If there is no DTC P0450 displayed EVAP system diagnostic has run and passed, indicating no malfunction was present this time. DTCs MUST be cleared to view CURRENT STATUS of the system diagnostics being performed. I/M System Information tests only indicate the test has run, not if the test passed or failed. The LAST TEST FAILED screen must be checked for related DTCs to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the sensor electrical circuit. Check wiring harness and components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set.