Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Hi
I'm looking for some information for a 2003 Chevrolet Monty Carlo SS. I was ask to diagnose a friends car. To make a long story short had a very lean condition.
Hidden under the wiring harness on top of the upper intake manifold plenum just behind where the throttle body bolts on there was a dime sized hole melted in the intake directly above the egr tube. In diagnosing I also found there was no 12v power to the egr valve.
I traced the wire to the ecm and no power there either.
Questions I have are what caused the egr gas to melt the manifold. Is it a plugged exhaust I'm waiting for a back pressure gauge or a fault in the ecm that kept the egr valve open. I checked the egr valve and the plunger was moving freely. Also is the 12v power to the egr fused anywhere or is the ecm driver fried. Currently no codes.
Thanks
Dave B56
I can answer the 12v question part. GM in one of the years, switched the Linear EGR valve to a power side switched circuit. They used to be ground side switched, so you would have a constant feed on that design. So I would say it is nornal and you need to command the valve to open to see the 12v you were looking for. Make sense?
To tell if it's power side switch I could either connect test light to pos. battery terminal and switch ground wire if it lights it would be power side switched or check continuity from ground to switch ground. Is that correct?
Next is to find out why the egr was open so long. I'll wait for back pressure gauge before going any farther.
THANKS
Dave
Topic Author
