Diagnostic Aids

Check for the following conditions:

• Poor connection at the ECM. Inspect harness connectors for the following conditions:
  • Backed-out terminals
  • Improper mating
  • Broken locks
  • Damaged terminals
  • Poor terminal-to-wire connection
• Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Vacuum Pressure display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.
• Incorrect purge or vacuum source line routing. Verify that the source vacuum and purge lines to the EVAP emission canister purge valve are not switched.