joncheryl

I sincerely apologize if the answer is obvious but I searched here and other places and couldn't find what I was looking for. 2001 Suburban 5.3L with only the code P0401 - Insufficient Flow through EGR system. From reading online, usually this is cause by carbon buildup in the egr passages or at the manifold. On my truck, it's all clear. If I manually actuate the EGR valve at idle (I don't have a two way scanner), the engine runs really rough and will stall. If the EGR valve wiring was bad, I'm pretty sure I'd get another code, like "incorrect pintle position" or something of that nature. The only thing I can think of is that perhaps the way the computer calculates EGR flow is bad but I don't know how EGR flow is calculated (MAP/MAF sensors???) and I would think if sensors were bad, I'd have another code like "engine too lean/rich". I moved and need this to pass emissions in Utah. But even more than that, I want to just know what's going on. Any ideas?

Thank you carnau. Helpful reply. I was using a plain non-LED test light and there was no corrosion at any connector. Just to conclude this for the potential future reader, my findings were sufficient evidence that the ECM was bad. I ended up buying a remanned ECM for $90 from flashmastersecm.com and no more misfires. I did have to go through a security sequence thing that was simple (you can youtube it) and I didn't have to do a "crankshaft variation" reprogramming. No core charge either.

2000 Suburban 5.3L. I'm having problems with the injector circuit for cylinder 3 in my car. I removed the connector on the injector and verified that it's getting power (constant 12V when key in ON position and 14V when engine is running). When a test light was put on the ground terminal it illuminated but didn't pulse. When I looked at the voltage though, it was bouncing all over between 0 and 14V. I turned the car off and noticed the ground terminal had 1.7 kOhms resistance to ground when the engine is off. Thought that was funny as it shouldn't be connected to ground when the car is off and if there was a short, the resistance should be 0. I traced the wiring and didn't see anything wrong. I then found a diagram for the ECM connectors, located the terminal for the cylinder 3 injector (ironically terminal #3) and found the same 1.7 kOhm resistance to ground at this terminal. This was the terminal on the actual ECM not the wiring harness. 1. Is this sufficient evidence that the ECM is bad? 2. Can I just go to a junkyard and pull an ECM out of another 2000 Suburban with the 5.3L and put it into my car with no problems? 3. If not, does anybody have experience with flashmastersecm.com? Judging from ebay, they look reputable.