Circuit Description

PCM will test the EVAP system for large and small leaks (P0440 and P0442), excess vacuum (P0446), purge during non-commanded operation (P1441), fuel tank pressure sensor and fuel level sensor faults (P0452, P0453, P0462 and P0463), and EVAP purge and vent faults (P0443 and P0449).

PCM monitors amount of vacuum in the EVAP system by monitoring the fuel tank pressure sensor. For the test, the PCM turns off the EVAP purge valve and turns on the EVAP vent valve when conditions for running the DTC have been met. This test indicates a leaking EVAP purge valve or flow during non-purge if fuel tank pressure sensor indicates increasing fuel tank vacuum. DTC will set after 2 consecutive failures of these tests and an increasing vacuum in the EVAP system is monitored.

Conditions for running this DTC are: no misfire, fuel trim, injector control circuit, AIR, ECT, EGR, HO2S, IAT, MAF, MAP, TP or VSS DTCs are set. Battery voltage 5-18 volts, BARO pressure greater than 75 kPa, fuel level 15-85 percent of full capacity for at least 10 seconds, ECT and IAT at start-up between 40-86°F (4-30°C), and ECT not greater than 46°F (8°C) or less than 36°F (2°C) of IAT at start-up.