EPR Vacuum Circuit Check

The Exhaust Pressure Regulation (EPR) solenoid controls vacuum to EPR valve. When energized, EPR solenoid allows vacuum to close EPR valve, increasing exhaust backpressure for proper EGR operation.

1. This tests for normal EPR vacuum at idle. Since electrical circuit was already proven okay in EPR SOLENOID ELECTRICAL CHECK chart, absence of vacuum is due to no vacuum source (vacuum pump), or a restriction or leak in vacuum hose to valve, including a leak in solenoid.
2. EPR solenoid is de-energized, no vacuum should be present.
3. This tests for normal operation of EPR valve. When vacuum is applied to vacuum valve, valve actuator should move and hold.

Fig 1: EPR VAC Check, Schematic

Courtesy of GENERAL MOTORS CORP.

Fig 2: EPR Vac Check, Flow Chart

Courtesy of GENERAL MOTORS CORP.