Diagnostic Aids

Carbon release from the EVAP canister could cause the purge valve to stick open intermittently. Check for carbon release in the EVAP system. If carbon is present, see EVAPORATIVE EMISSION SYSTEM CLEANING in REMOVAL, OVERHAUL & INSTALLATION.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.