A GM with an EGR fault, That isn't a surprise. There are two common failures on them, the coil in the electronic solenoid that controls vacuum to the valve fails and cannot control the valve or the valve itself sticks and causes issues. As you have the code but not drivability problems it's likely the solenoid or the wiring to it. Attached are the wiring and the OE tests for that. The code can be set by a bad connection, loss of power to the solenoid or the PCM has an internal failure. A really simple way to test the system is to take a test light and check that there is battery voltage at terminal A (Pink w black stripe) on the connector. Then if it is good you connect the test light in place of the solenoid and go for a drive while watching the light. The EGR isn't on all the time so the light will stay off when the PCM doesn't open the valve. Then it will come on when EGR is called for. So if you are driving normally and the light comes on and goes out in a sort of random fashion, the PCM and wiring are good. That would tell you to test the solenoid. For that you just apply battery power to it. Before that you try to blow through it. Without power it should be closed, if you can blow through it, toss it in the trash and replace it. If you apply power and cannot blow through it, toss it in the trash and replace it. I only wish modern cars were that easy.
Oh, if you intend to keep the truck a while, look into buying a Snap-On MT2500 (Brick) scan tool. They would plug in and let you do some testing like this without needing to touch things first. They were and still are a great tool for the pre OBD II vehicles (and some later) and used you can get them for a couple hundred off auction sites. Just be sure to get the correct cartridges and cables.
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Saturday, March 21st, 2026 AT 11:30 AM
