ABS and brake light stay on

Tiny
THENIGHTOWL
  • 2001 CHEVROLET ASTRO
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 44,000 MILES

I have a 2001 Astro van with 44000 miles. The other day the ABS light came on. After parking and turning the key off, then back on and driving, it would be off for about 30 minutes then back on again. Then the next day it came on along with the red brake light warning. I adjusted the rears, topped off the ms and topped off the power steering rez. It did not come on after that for a day. Now they are both back to on all the time. I have checked the entire system without finding anything out of whack. Any ideas?

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Friday, April 15th, 2011 AT 8:41 PM

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Tiny
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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.

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Friday, April 15th, 2011 AT 8:51 PM
Tiny
RASMATAZ
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Could be caused by one of the following below

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it and keep testing

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Friday, April 15th, 2011 AT 8:52 PM
Tiny
RASMATAZ
  • MEMBER

Wrong question -sorry Doc cannot delete

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Friday, April 15th, 2011 AT 8:54 PM
Tiny
CARADIODOC
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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!

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Friday, April 15th, 2011 AT 9:00 PM
Tiny
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I finally got the code read, and it says co265 ebcm malfunction. The problem with that is I can find hardly any info on what values to check for. They are tight-lipped in my area and I had to pull teeth to get a free read. What I have done so far since the read, is cleaned the front wheel sensors. Even the backside of the sensor mount, checked all conectors, and made sure power is at the module.

I did notice that both the module/pump and sensor wiring is too close to the exhaust IMO. I also notice the lights come on when its hot under there. In the mornings they're off until I get some mileage, then if I let it sit and cool down, the lights are off on restart. Go back to driving for a bit, lights back on. Maybe. Yesterday was cool and real windy and the lights stayed off until it sat inside for 20 minutes, then back on until the next restart.

The replacement module is $1124.26 ! And I don't even know if thats the culprit. Should I try to get the code read while the error lights are on?
Is there a way to make the pump work without finding a dirt road to where I can hear it kick in while the error lights are off?

I know this is not a serious problem, but its driving me nuts and I have to figure it out.

The only change I have done is hauling much more weight in the last 3 months, and just before this went wacky I started smelling the nice rotten egg smell from the cat. Thats why I'm leaning toward a heat related problem. I doubt its the speed sensor in the tail end of the trans, and the brakelight switch seems a bit out there too.

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Wednesday, April 27th, 2011 AT 12:48 AM
Tiny
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Edit: Rotten egg smell ALONG with hearing the exhaust popping and cracking while cooling down which I have not noticed before.

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Wednesday, April 27th, 2011 AT 12:52 AM
Tiny
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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
Tiny
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Today I cleaned and made sure all the grounds I could find were secure. Drove it for a bit and the lights were off. I connected a volt meter to the front wheel sensor leads and got 2.65 volts on each wheel sensor seperately and that was by turning each wheel at a somewhat fast constant speed to make it easier. If I tried the one rev per second deal it was hard to get a good read. From what I have read, the voltage should be a minimum of 350 acmv's, but my tester doesn't do milli so I had it on normal scale ac. Then I drove it again. Lights still off.
I unplugged the wheel sensor connector and started it up. Immediately had both lights on. Plugged them back in, started it up, both lights went off, so I have to assume the front sensors are fine. I did the same thing with the sensor on the tail end of the trans. Same results so I have to assume that sensor is also fine.

Then I drove about 4 miles and parked it while the lights were still off. Got back in 15 minutes later and both lights were on. I drove another 7 miles and shut it off. Got back in maybe 10 minutes later and the lights were off all the way back home which was another 7 miles.

My next test will be while the lights are off. I will brake hard on a dirt road and see if the pump kicks in. If it does? If it does not, then would the pump be faulty? Notice I'm staying away from the module until the last resort!

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Sunday, May 1st, 2011 AT 12:31 AM
Tiny
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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.

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Sunday, May 1st, 2011 AT 2:36 AM
Tiny
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When I pulled the rotors I cleaned inbetween each grove on the tone rings and never noticed any cracks. The only thing I did notice was that the rings were quite shiny from turning? Against the sensor's mounting face. Also, the mounting surface was not worn in any bad way to effect anything, the shine was probably due to crud between the 2. If there were any cracks they should? Have been easily noticable because of the crud that would have built up in the crack. Now that I said that, and along with the heat issue I believe might be the problem, it IS possible there may be a crack that only appears when that ring gets hot and expands. I didn't like the construction of the sensor and it's flimsy mounting process either. The rubbing was slight and there was a small amount of crud behind the mounting face that I assume caused the rub in the first place. Either that or the boys in mexico placed both rings too far out, but if that were the case it should have left the factory with the code already set?

I feel like an idjit for not asking the guy who scanned it to erase the code!

I will try to get him to erase the code/s sometime this week, and start from the beginning if the code sets again.

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Sunday, May 1st, 2011 AT 7:56 PM
Tiny
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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.

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Sunday, May 1st, 2011 AT 9:34 PM
Tiny
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OK, so I took it to another shop for a scan. The guy told me the battery only had 500 milliamps. Yes, I wrote mili, and he said that was most likely the problem. I asked him if it were that low how did he start it to bring it around back? Them crickets were really loud!

The only thing he contributed was that the front sensors were fine which confirmed my own test. I didn't even ask him if he cleared the co265 code because when I asked him if that's the code he got, he looked all confused and asked what that meant. Arrrg! He even left the awesome scanner plugged in and sitting on the seat when I got in to leave. He's lucky I'm honest! But it did say "ebcm malfunction" before I unplugged it and took it back in. If I knew how to run it I would have cleared the code because the lights were still off.

So what I have done to date is change out the rear speed sensor located in the tail housing of the trans (The tech told me it was in the diff). Now it only shows the fault lights every other time I start it up and go, and the lights no longer come on while driving, just when I shut it off and go again. When I pulled the old one out, there was dark grey slime on it that smelled burnt. The oem sensor has a brass cap covering the actual sensor where the replacement is plastic. I'm now really leaning towards a heat related problem since the rear sensor change had an effect that was noticeable, brass/copper holds heat longer than plastic, and the change in lights off/on stayed constant all weak. I do deliveries and my route and mileage is the same every day. The only difference is the amount of time I'm inside a customers place. The longer I'm inside, the more chance that the lights are off when I leave. To me that means the heat is disipating while it sits. The shorter I'm inside the chances are the lights come back right after I start it. To me that means the heat has not had time to disipate. If it were the exhaust or engine heat, it seems it would get worse when it sits and the heat sinks in, so I'm leaning towards the heat in the trans fluid. Does that make sense?

The trans fluid is not burnt like that in the tail housing? Now I'm thinking that slime contains metal particles biulding up at the tail that are throwing off the sensor? New filter and fluid are obvious next step but cleaning that end I'm prbably going to have to remove the tail housing to do it.

I went to modulemasters site but something seems a bit fishy? If you do the diagnose test online, it ends up telling you its a problem they have yet to encounter if you stay clear from clicking the yes button when it asks if the +- connections were bad. If you click on the faq where it says "Can I fix this myself" it only talks about fixing the +- connections at the module/pump? So is that all they repair? I'll be snooked if I send in my module and they say nothing was wrong with it because all they fix is the connectors. Has anyone here used them?

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Saturday, May 7th, 2011 AT 9:53 PM
Tiny
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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.

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Saturday, May 7th, 2011 AT 10:16 PM
Tiny
THENIGHTOWL
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True, but heat also expands and contracts those coils changing inpedence which 'could' change values sent to the computer. As soon as by back straightens out (thats why it takes so long to get back here) I am going to either insulate the computer or install a small fan. Same thing with the module to see what happens. I also thought I would add a few grounds. One thing to note: Our air temp here has risen 20-40 degrees in the past week so I thought it would be worse not better. Then again, I'm not smashing the peddle and doing my route slower to stay out of trouble;)

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Saturday, May 7th, 2011 AT 10:57 PM
Tiny
NCPATSFAN
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Just my 2 cent. I feel you angst. The Kelsey-Hayes EBCM is notoriuos for failures. The C0265 ABS code is for a fault in the relay circuit. Unfortunately for this ECBM it is inside the EBCM. The likely reason it only acts up when hot is the relay shorts out when it gets hot under the engine. Mine is doing this as well in a 2001 Blaszer. I have a Kelsey-Hayes 325 module. Modulemaster. Com will rebuild your EBCM for $130 rather than a new one if your ECBM is one they can repair. Check out their website. I have not used them but others on the Blazer forums have and they appear to have a 5 yr warranty on rebuilt ECBMs they do. I added an image of what mine looks like (removed from my Blazer). Not sure on your vehicle where it will be. Likely on the drivers side near the brake fluid reservoir area. Good luck and I hope this helps.

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Monday, July 18th, 2011 AT 1:14 PM
Tiny
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I have the repairable one, but my post above 5/7/2011 was talking about modulemasters. From what I can tell by going through their site, is that they only repair damaged connectors? It would be a waste of money to have that done if the circuitry was the issue.

I do know for certain its a heat related problem. The lights come on just after 5-10 minutes of driving now, and stay on all day until I shut it down for the night.

I can either live with it or buy the Jet programmer to just shut those 2 error lights off for good. Its seems cheaper than giving modulemasters $130 to find nothing wrong there, then another $120-$200 for another computer hoping THAT was the problem, then spending the $$ for the programmer. Then again, I could just pull those 2 bulbs or put tape over those spots on the dash panel.

I love a challenge, but this one blows!

The only thing I have not checked out is the proportional valve switch. But if it were that, I would probably know it by now.

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Monday, July 18th, 2011 AT 6:34 PM
Tiny
NCPATSFAN
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My understanding is module masters opens up the module that is causing the problem and rebuild the broken components. Bad relay etc. With a new relay or broken components. They claim to replace and or upgrade known to fail parts. I am not sure but the testimonials seem good and the 5 year waranty to boot. If the module is unrepairable they claim to send it back to you. I have not used them so I can not speak first hand. Currently trying to do this on my own. Have my Kelsey- Hayes 325 opened up and am replacing the relaya with a new TE conectivity relay P/N : PB380-ND $ 1.68 each TE Connectivity Mfg Part #: T7NS5D1-12
I ordered from digikey. Com yesterday. If it works I will send you a how to I am writing up. If this works you need a relay ($1.68 + shipping) some solder, some heat sink compound ($4), some silver solder and time/patience.

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Monday, July 18th, 2011 AT 8:04 PM
Tiny
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That would be great!

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Monday, July 18th, 2011 AT 8:36 PM
Tiny
NCPATSFAN
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FYI TheNightowl, I got my new relay above, soldered it in and resoldered the pins on all conections I had de-soldered earlier. Put heat sink on spots needed, siliconed case seal and put back in. Cleared old ABS C0265 code and drove around for 1 hr in 100 degree NC heat. This would usually give me the code back due to extreme heat. ABS code did not come back yet, crossing my fingers. This may have worked. Since it was intermitent to begin with I will not know for sure until I get to drive it some more. I am writing up a powerpoint presentation with annotated photos. I if you want give me an email to send it to. I wont be able to get to this until monday 7-25-11

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Friday, July 22nd, 2011 AT 11:07 AM
Tiny
NCPATSFAN
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TheNightowl. I did a writeup of the repair I did on friday. It worked great. No ABS or brake light since fix. It has benn 100+ in NC where I live and it would have normally come on multiple times. I have a powerpoint I could send on how to do this. Just let me know where to?

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Monday, July 25th, 2011 AT 3:29 PM

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