Diagnostic Aids

Although this DTC is considered a type A diagnostic (refer to "Engine Control Module"), it acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately. Check for the following conditions:

• Poor connection at ECM. Inspect harness connectors for the following conditions:
  • Backed-out terminals
  • Improper mating
  • Broken locks
  • Improperly formed
  • Damaged terminals
  • Poor terminal-to-wire connection
• Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, connect the EVAP emission pressure/purge cart to the EVAP emission service port, pressurize the EVAP emission system to 10 inches HO2S2 and observe the Fuel Tank Vacuum Pressure display on the scan tool while moving connectors and wiring harnesses related to the EVAP emission canister purge valve. A sudden change in the display will indicate the location of the fault.
• Incorrect vacuum line routing. Verify that the source vacuum line routing to the EVAP emission canister purge valve is correct and that the EVAP emission purge and source vacuum lines to the EVAP emission canister purge valve are not switched.
• Loose Carbon in the purge solenoid. Blow out the following conditions: lines and replace the purge canister.