EVAP System Diagnostics

Diagnostic Chart Part 1:

Diagnostic Chart Part 2:

The ECM monitors the following EVAP system electrical components for open, low and high voltage faults:
^ Fuel tank pressure sensor signal
^ EVAP purge solenoid
^ EVAP vent solenoid
^ Fuel level sensor signal

As part of the On-board diagnostics second-generation (OBD II) requirements, the government mandates that all automobile manufactures detect a 0.040-inch or greater diameter leak in the EVAP system. To comply, the ECM monitors the EVAP system for large and small leaks and whether the EVAP purge and vent solenoid valves are stuck closed or open.

IMPORTANT: The following flowchart consists of a series of tests run by the ECM, which describes the entire EVAP DIAGNOSTIC TEST. Each step the ECM performs is dependent on the accuracy of the fuel tank pressure sensor. The FTP SENSOR reading on Scan tool with ignition On, engine off and fuel cap removed should read between 1.40 and 1.60 volts.