ABS and brake warning light stay on

There will be at least one diagnostic fault code stored in the ABS computer. Having those codes read will get you into the right circuit or system.

The brake fluid shouldn't be filled. If it was excessively low, either there is a leak that must be addressed or the front disc brake pads are worn to the point of replacement. When you push the pistons back into the calipers to make room for the new pads, that fluid is going to overflow and make a mess.

No need to apologize. Since we lost the ability to delete our own replies, we're all posting all over each other. I don't bother to apologize anymore and I don't expect any in return. I'm not offended when other people add their thoughts. It's just the nature of this new format.

Have a dandy, ... Uhm, ... Lets see; what day is it? Oh, have a dandy Friday!

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.

Now I have to defer to my Chrysler experience but even then I didn't work on their systems very often. Pulling a connector, as you found out, is detected as an open electrical circuit during the six-second self-test when you turn on the ignition switch. All you can be sure of when the warning lights do not turn on right after that self test is the electrical circuit has continuity. If the air gap is wrong, the tone ring is cracked or missing, or there's a problem with the sensor's magnetic core, that won't be detected until the van is moving and the computer sees the signals from the other sensors.

Here is where I see a potential problem. On some vehicles the ABS computer can only store one diagnostic fault code. There might be one in your computer now from the first time the warning light turned on. On some of those older systems the codes do not self erase after a certain period of time if the problem doesn't return. They have to be erased with a scanner, and until it is, the computer can't set a new code when necessary. The frustrating part of this system is that when the first problem is corrected and the code is erased, the computer is able to set the next code and turn the warning light on again. Now you have what appears to be a new problem and it's often blamed on the mechanic who performed the first repair. That can go on and on if there are multiple problems. This rarely happens when you take the vehicle in right after the light comes on because that second or third problem hasn't had time to develop yet. It happens more often when people ignore the warning light for months or years.

More advanced computers can store multiple codes. Being a three-channel system, I suspect this pertains to your van. The thing to be aware of is there is always a set of conditions that must be met for a code to set. One of those conditions is that certain other codes are NOT in memory already. As an example, the computer will not set a code for mismatched wheel speeds if there is already a code for loss of signal from one sensor. It knows it has no reliable signal to compare to so it won't set that code. Likewise, you are going to have three codes related to open circuits to the sensors you unplugged. Even though the light is off now, those codes are still in memory. I don't know what will happen with any new problems that are detected. They might be recorded when everything else is working, or they might be ignored because of the existing stored codes.

The place to start, if you have access to a scanner, is to read and record all of the stored codes, then erase them and drive it until the light comes back on, then read them again. If you come up with a list of codes, you should be able to figure out which ones were set from unplugging sensors. Those can be ignored.

Another thing to consider, which I would never recommend for 2002 and newer vehicles, is to disconnect the battery cable for a minute to try to erase the codes. Some vehicles can not have their codes erased that way. Even unplugging the computer will still keep the codes stored. Those must be erased with a scanner. If yours DO erase, there will only be the one current code if you drive it until the light comes back on.

In my limited experience, if a tone ring is cracked, you'll see it. You won't have to guess. It will usually be loose enough that you can spin it by hand. I had a cracked one on my mother's '95 Grand Caravan. I used that as a demonstration for my students that it is possible to weld cast iron. I don't remember what the code was but each time the engine was restarted, it took from 100 feet to a couple of miles before the warning light would turn on. That was a "latching" code which meant even if it was an intermittent problem, the light would "latch" on and not turn off until the ignition switch was turned off and back on.

Will wait to hear what you find.

After talking with some other people, it seems GM does have a lot of computer trouble but I hate to recommend getting a different one without knowing for sure yours has a problem.

As far as repairing yours, I'm sure they do more than clean connections but I always worry about intermittent problem. I know from experience what to look for in some car radios that commonly cause intermittent problems so I'm pretty sure those guys know too what to look for in that respect. I would feel better if they stated in their web site that they routinely repair "this" and "this" and "that" and "intermittent fault code XX". At least that would show they know what to look for.

You are right about heat buildup, but worse than the sensor, heat is the deadly enemy of electronic components such as transistors and integrated circuits. Based on the original code you were getting it's more likely the heat issue is in the computer itself, not the sensor. Most ABS speed sensors have only two wires which means they just have a coil of wire wrapped around a magnetic core. There is no electronic circuitry in them to become heat-sensitive.