I've seen controller codes before when the system was working fine otherwise, so I wouldn't jump at the module just yet. The heat issue is one possibility but rather than looking at wires, it's more likely to affect electronic circuitry such as the computer. Heat-related problems were half of what I used to search for when fixing tvs.
Something else to consider is that eventually an electrical problem will be detected during the self-test when you start the engine. If the hot exhaust is causing wires to melt, that is going to continue to get worse and the problem will be detected sooner than after a half hour.
Something else to look at is the tone rings by the two front wheels. If one is cracked, that won't be detected until after the vehicle is moving. At first the extra pulse from the crack might be rationalized as the vehicle is going around a sweeping curve, but eventually the computer will realize there's a mismatched wheel speed and will turn on the light. The memorized code will be different than what you're getting, but there are conditions that must be met for any code to set. One of those conditions is that certain other codes are not already in memory. The computer compares many things to determine when there is a problem, and if the things it's comparing something TO has a problem, it knows it can't use that to test something else. For that reason, sometimes a new fault code will show up right after the previous one was repaired.
Now that I confused you with all of that, I'm inclined to think something inside the computer is getting warm and causing the internal fault. GM has a real high failure rate of the ABS computers on the trucks but I haven't heard of that on the Astro Vans. Also, that applies to the four-wheel systems, not rear-wheel systems.
Before you spend that kind of money for a computer, you should consider finding one at the "pick-your-own-parts" salvage yards. If you're between Indianapolis, Ohio, and southern Georgia / Alabama, there is a chain of very clean and well-organized yards and the parts are very inexpensive. With a warranty you can expect it to run around 50 bucks.
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Wednesday, April 27th, 2011 AT 2:51 AM