EPR Solenoid Electrical Check

WARNING: This page does not describe the selected car, but rather 22 other vehicles, including the 1992 GMC Yukon, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Value Van, and 1992 GMC Rally Camper Special. However, it is still accessible from the selected car via links, so may be relevant.

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. The solenoid is supplied with 12 volts by ignition switch. ECM completes ground circuit to energize solenoid, and turn EPR on when needed (EGR operation command).

NOTE: Test numbers refer to numbers on diagnostic chart.

This tests for short to ground, or a faulty ECM signal to EPR solenoid. Test light should normally be off.
This tests for signal to energize EPR solenoid with engine at idle. If test light is on, electrical circuits to solenoid are okay.
This tests for voltage, or open circuit from terminal "B" of EPR solenoid to ECM terminal C12.

Fig 1: EPR Sol Elec Check, Schematic

Courtesy of GENERAL MOTORS CORP.

Fig 2: EPR Sol Elec Check, Flow Chart

Courtesy of GENERAL MOTORS CORP.