Vehicle applicability: This diagnostic supplement covers multiple Ford vehicles and engines. Follow the application named in the source below. Some references apply to vehicles other than Mustang.
Description and Operation 1-119
Evaporative Emission (EVAP) Leak Check Monitor
A step change logic becomes active after the 4th EONV monitor test. The step change logic detects an abrupt change from a no leak condition to a suspected leak condition. The MIL illuminates if the PCM suspects a leak within 2 consecutive trips using the step change logic. During the EONV monitor test the PCM uses an exponentially weighted moving average to filter test data. The PCM uses this average after the fourth EONV test and illuminates the MIL on the first trip when the exponentially weighted moving average is greater than a calibrated threshold. When a leak is suspected a DTC sets and the MIL is illuminated. On non ISO 14229 vehicles, when a leak is suspected, the PCM uses the stored fuel tank pressure and time since ignition OFF information from an average run of 4 tests to suspect a leak. Some vehicles use an alternative method of a single run of 5 tests to determine the presence of a leak. If a leak is still suspected after 2 consecutive runs of 4 tests, (8 total tests) or one run of 5 tests, a DTC sets and the MIL is illuminated.
5. The EONV EVAP leak check monitor is controlled by a separate low power consuming microprocessor inside the PCM. The fuel level input, fuel tank pressure, and battery voltage are inputs to the microprocessor. The microprocessor outputs are the EVAP canister vent valve and the stored test information. If the separate microprocessor is unable to control the EVAP canister vent valve or communicate with other processors a DTC sets.
6. The MIL is activated for any enhanced EVAP system component DTCs.
EONV EVAP Leak Check Monitor
2016 Powertrain Control/Emissions Diagnosis, Gasoline Engines, 3/2015
2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.