What size engine in your Jimmy?
This is something you can do yourself. The EGR valve is located at the top right of the engine next to the throttle body.
Remove the EGR valve, and using carb cleaner, spray inside ports of EGR valve, and use a small tooth brush or pipe cleaner to clean out the ports of carbon buildup. Always use a new gasket when removing the EGR valve.
REMOVAL & INSTALLATIONExcept Linear EGR Valve
See Figures 11 and 12
Linear EGR Valve
Note the position of the EGR valve prior to removal. Do not rotate the valve 180º.
Sorry, forgot to include resetting the codes:
Ok, you have a linear EGR valve then. Should be bolted to top front of engine at intake:
Spray carb cleaner in port hole and use brush to clean out any carbon buildup. Make sure the pintle(the silver part on the bottom of photo above showing bottom of egr valve) is clean of carbon build-up.
Clean carbon build up out of port hole where egr valve bolts to .
On the linear EGR valve, if it is throwing a code every few weeks and having to be cleaned, you may need to go ahead and replace it.
Also, you want to clean carbon build up out of throttle body, and run a good top end cleaner to remove carbon buildup from injectors and valves.
DO YOU HAVE PICTURES OF THIS TYPE EGR ON THE ENGINE?
Here is one. It is located at top front, between the alternator and the compressor-#5 in photo:
Here is a diagram showing the egr close-up: