This type of EGR Valve has made the auto repair industry and GM a ton of money over the years, since it's prone to carbon blockage. Well the good news is that this is an EGR Valve and EGR Valve System that is very easy to test and diagnose... and this article will walk you thru' the entire diagnostic/troubleshooting process.
General Motors has used different types of electronic EGR Valves and this article focuses on the Linear EGR Valve from the mid 90's to the early 2000's. How can you tell them apart? By looking at the base of the EGR Valve. To illustrate this, look at photo 3 of 4 and photo 4 of 4 in the image viewer above.
The EGR Valve in photo 3 of 4 (with the RED X) is not covered by this article and is tested differently. The EGR Valve in photo 4 of 4 (with the GREEN check mark) is the one covered by this article. If you need the EGR Test for the EGR Valve marked with the X, you can find it here:
You can find this tutorial in Spanish here: Cómo Probar la Válvula EGR de GM (Buick, Chevrolet, GMC, Oldsmobile, Pontiac) (at: autotecnico-online.com).
This is not the most definitive list on the subject, but does cover the majority of symptoms I've seen on this type of EGR Valve Setup:
When something goes wrong with the EGR System... you usually see one of the following:
This article will help you to diagnose all of the above DTCs, since it covers how to test the EGR Solenoid (which I call the Pintle Motor), the EGR Pintle Position Sensor and carbon blockages (the EGR Solenoid and Pintle Position Sensor all are inside and part of the EGR valve itself).
A Scan Tool (Automotive Diagnostic Scanner) isn't needed to test the EGR Valve on your GM car or truck. I'll show you how to test it without expensive tools. Here's what you'll need:
The connector on the EGR Valve has 5 wires and normally the letters A thru' E are stamped on the EGR valve itself (but not always). I'll be using these same letters in all of the photos in the image viewer so that you'll know what wire to test. Below are the circuit descriptions:
The color of the wires is not important as long as you identify the wire (circuit) by its letter designation. Also, the EGR Valve on your vehicle might have its connector connecting to it at a 90 degree angle or connecting straight down onto the EGR Valve. This is also no cause for concern since they are one and the same when it comes to using this info to test them.
To test these circuits, it's not necessary to unplug the EGR Valve's connector. What I recommend you do is to test for each signal with the connector connected using a Wire-Piercing Probe. This is the easiest and the most effective way of getting at the signals. If you need to see what this tool looks like, click here: Wire-Piercing Probe.