EPR Vacuum Circuit Check
The Exhaust Pressure Regulation (EPR) solenoid controls vacuum to the EPR valve. When energized, EPR solenoid allows vacuum to close EPR valve, increasing exhaust backpressure for proper EGR operation. When vacuum is applied to the actuator, the restrictor plate closes to increase exhaust system backpressure, allowing EGR valve to function more efficiently.
Test Number 1) This tests for normal EPR vacuum at idle. Since electrical circuit was proven okay in prior flowchart, if no vacuum is present, it is due to no source vacuum (vacuum pump), a restriction or leak in the vacuum hose to valve, including a leak in solenoid.
Test Number 2) The EPR solenoid is de-energized, so no vacuum should be present.
Test Number 3) This tests for normal operation of EPR valve. When vacuum is applied to vacuum, valve actuator should move and hold.