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carhelpguy
carhelpguy, ASE Certified Tech.
Category: Chevy
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Experience:  Over 15 years of experience working on GM, Ford, Chrysler, Toyota, and Honda. Diesel and Electrical specialist.
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1999 Chevy Suburban: 6.5 diesel..2500/4x4..The cruise control..ECM

Resolved Question:

i have a 1999 Chevy Suburban 6.5 diesel/2500/4x4 with a cruise control problem. The cruise control went out about 3 weeks ago, and hasn't worked since. I checked for any ECM codes and came up with nothing. I checked the fuse which was fine too. I replaced the cruise/blinker/hazard assembly about two months ago and it worked fine up until 3 weeks ago. I got up under the dash tonight and found a purple/white stripe with hanging on the opposite side of the steering wheel that i don't remember seeing before. It's about a 14 gauge wire that has bare/exposed wire at the end. Any idea what might be going on with the cruise??

Thanks,
Jim
Submitted: 4 years ago.
Category: Chevy
Expert:  carhelpguy replied 4 years ago.
Thank you for your question. I hope I can help.

I was looking into your concern and this system is pretty simple to test. Looking at the schematics I could not see a purple/white wire going to any of the cruise inputs. However I did find one which is a VSS signal at the vehicle speed sensor buffer. This is a small box located to the left of the glove box and has a 12 pin connector on it. However it the input from the VSS sensor so your speedometer would not work if there was a problem with it.

Do you have access to a test light and a volt meter? If so run these tests.

Test, with a test light, for power on circuit 397 with the cruise switch on as well as power on 87, and 84, when pressing the resume and set switches, all at the cruise switch and at the PCM.

Then, at the brake switch, test for power on the purple wire (circuit 420) the brake pedal released and, using the meter make sure it is 0 volts with the brake pedal depressed. Perform same test at the PCM.

Next test for 0 volts, using a meter, on circuit 17 (white wire at brake switch) with your foot off the brake and 12 volts with pedal depressed. Also repeat test at the PCM.

The last test is the hertz reading on the VSS signal circuit 389 (dark green wire) at the PCM with the vehicle in motion. I assume that the speedometer is working so the VSS buffer should be working however the wire could be open to the PCM. You can also test that circuit for an open between the buffer and the PCM.

Let me know what you find or if you need more info. I have also attached a schematic to help out.


Thanks,
Mike



graphic
Customer: replied 4 years ago.
I checked late last night and traced the purple/white stripped wire to my remote starter/security system. From what i found out in the installation manual, the purple/white stripe wire is supposed to be a tach wire. I'm not sure what that would have to do with the cruise control though. I'll try sending you the schematic so you can check it out. Ok i can't get anything to attach here, so here's the web address where the manual is. It's on page 57
http://www.directeddealers.com/manuals/ig/hornet/N563T_09-05.pdf

Where is it that i'm supposed to check those circuit numbers you mentioned?

thanks!
Jim
Expert:  carhelpguy replied 4 years ago.
Ok. Thanks for sending the manual. Looking at the manual the only thing the wire should affect is the remote starter itself. This should not affect the cruise. However the remote starter requires being wired into the brake switch for the brake input and should be a brown wire that would normally be tapped into the white wire at the brake switch. I would check that wiring first. If the remote starter has internally failed it will send voltage out unwanted on the white wire (circuit 17) making the PCM think your foot is on the brake.

To run all of the tests I would start at the cruise switch and at the brake switch (depending on which circuit you are testing). These components are easier to get to in most cases and are a whole lot easier to identify which wire does what unlike the PCM which has many terminals in the connectors.

When testing these circuits I like to leave the component connected and backprobe the connections. Also does the scanner you used for codes also check data. If so check the PCM data for brake switch activity as well as TCC brake switch data.

Let me know
Thanks,
Mike
Customer: replied 4 years ago.
Hey Mike,

I'll check that stuff out, although haven't ever checked the components before. I have a 12volt test probe, i assume that's what you're meaning. So basically i tear the steering column apart and use the tester there?

Would the speed sensor be a possibility?

The scanner i used did check all trouble codes, and ECM data as well. It came up with nothing.
Expert:  carhelpguy replied 4 years ago.
A test probe is good. Use that first. Start with the easiest components to get at first. I like to start simple. If you have checked all fuses in the schematic then the brake switch is where I would start and I have seen concerns with the brake switches in the past. Locate the brake switch and TCC switch data in the scanner and make sure they read applied and released as you press on the brake pedal and let off. The PCM needs both of these inputs and if not correct proceed with the voltage test with the probe at the brake switch.

I read that you replaced the "cruise/blinker/hazard assembly" I assume it is the switch assembly. If so, and if I remember correctly, this switch should go to a large square connector under the dash with a bolt in the middle of it. If it does then you can test all of the inputs from the cruise switch there. I like to test the PCM inputs last as it will take some time identifying the correct terminals.

The speed sensor should not be the problem as long as the speedometer is still working in the dash. The speed sensor is an input to the speed sensor buffer module which then sends it to the gages and the PCM. If all brake and cruise switch inputs are correct then we will have to use a meter to test the speed sensor circuit signal resistance and hertz signal. We will cross that bridge if we get there.
Customer: replied 4 years ago.
Ok, I've ruled out the brake switch/remote starter connection because if I use the remote starter and hit the brake it kills th engine as its supposed to.

I assume that checking the wires in the column, I can use the diagram you sent me to figure out what should be hot? Sorry I'm just a backyard mechanic with common sense! LOL!
Expert:  carhelpguy replied 4 years ago.
Not a problem at all. I am happy to help in any way I can. Trust me you are a lot further than some dealer techs I talk to at tech assist. One of the brake switch outputs is working as it does kill the remote starter but the other, more crucial input, will still have to be verified with the test probe(the purple circuit 420).

If you get stuck let me know I will walk you through any step you need.
Customer: replied 4 years ago.
Before I rip the column apart, what's your thoughts on the PMD going bad? I read a lot of forums where guys are saying that's what killed their cruise control. I relocated the mount on mine with a heat sync 2 years ago and it helped to keep it cooler...
Expert:  carhelpguy replied 4 years ago.
Me personally, I have not seen the injector driver cause cruise control issues. It is possible if there is an engine running concern or if there is a driveability trouble code involving the module. I have replaced several of these for unexplained stalling while driving and for certain codes, and I think there is a bulletin for that.
Customer: replied 4 years ago.
Ok so far, brake switch checks out, cruise wiring checks out, speed sensor is ok.. any other suggestions?
Expert:  carhelpguy replied 4 years ago.
Were all tests done at the component only, or did you also look at the readings at the PCM. If not tested at the PCM then I would like to go there next. To do this disconnect the PCM, with the key off, and then when disconnected turn the key on for testing.

Test the same circuits that were tested at the component at the PCM connector. If you could tell me the test light results on each terminal at the PCM in detail and then I will see what needs to be done next. I have attached the connector end views to help. These are pictures of the connector looking at the face of the connector with it disconnected.


Let me know



graphic


graphic
Customer: replied 4 years ago.
Hey Mike,
Ok I ended up taking it to a repair shop and gave them the info u gave me, they checked everything and said they think it's the PCM module because everything else checked out. They don't have the software available to check the PCM though...
What do u think?
Expert:  carhelpguy replied 4 years ago.
I was getting close to condemning the PCM myself with the tests we have run. Not to sure about the inability to check it though. I guess it depends on the scanner that they are using to perform the tests. Give them the tests that I gave you and have them verify the steps. If the data in the scanner you have indicates that both brake switch inputs are operating normally, there is a vehicle speed signal reading in the data, and there are no codes then I am comfortable with the PCM recommendation. Let me know what happens or if I can be of more assistance. I am always here to help.
Customer: replied 4 years ago.
Thanks Mike, I'll be in touch...I got a PCM on order.


Jim
Expert:  carhelpguy replied 4 years ago.
Not a problem I will be looking forward to hearing what was found.
Customer: replied 4 years ago.
Hey Mike,

Well I FINALLY received the ECM from Autozone (i'm not gonna go there!). Anyway, installed it tonight, did the Passlock relearn sequence, and fired it up. I took it for a ride and...NO cruise control. I got it back home and disconnected the batteries to clear any codes that might have developed in the new ECM. I hooked the batteries back up, fired her up, and it was like when you mix up plug wires on a gas engine! It was missing consistently, and if i touched the accelerator it would rev over 3000+ rpm's. So i'm guessing that the "flash" on the ECM didn't work very long. I threw the old ECM back in, still no cruise, but at least it runs! Any ideas on the cruise?

Thanks,
Jim
Expert:  carhelpguy replied 4 years ago.
Thank you for getting back with me. Yeah, Autozone and ECM's don't often mix, especially if they use a cheap rebuilder of the ECM. It sounds like it was not triggering the injector driver correctly. You were right to do the battery disconnect that was a good step.

I am going to have to research this further and get back to you later today. Just out of curiosity, what scanner were you using on this one? Also is there a way to capture data on the scanner and load it to a computer to possibly send it to me. One thing you could also try is take an actual picture of the data list and send it to me.

Let me know if this is possible and I will also get back to you later after my research.

Thank you for your continued patience on this one.
Expert:  carhelpguy replied 4 years ago.
Thank you for waiting. I am sorry it has taken a while to get back with you. I have contacted my resource in engineering to see if there have been any trends lately with cruise control problems and this year of vehicle and the only thing we were finding involved a code P1216. This is what you were referring to earlier in our conversation about the injector driver.

I would like to review the diagnostic steps for this one if you do not mind. For know lets start over.

First things first double check for any code in current or history status in the PCM. Also if possible get me the info from the scan tool as stated in the previous post.

Next, I need to get the voltages at the powertrain control module using a volt meter, if you have one, for connector C2 terminals A6 B9 and B10. If you do not have a voltmeter, check with your local parts store to see if they will rent you one. I have seen the ability to do this at Autozone.

Take these voltage readings with the PCM plugged in, and bagkprobing the connector using a hatpin. For pin A6 do the test while driving down the road as this is the vehicle speed signal.

Let me know the exact readings and I will do everything I can to figure this out.
Customer: replied 4 years ago.
Hey Mike,
No worries on getting back to me, been busy myself.

So starting over:

No codes on the PCM or anything else for that matter. The PCM has been relocated with a heat sync to the intake manifold to keep it cooler.

I don't know the name of the scan tool used, it belongs to a buddy who is out of town. I know it was an expensive one (2-3 grand range).

I'm not sure where the powertrain control module is, i do have a good voltmeter to check it though.
what is a "hatpin" i don't think i have one of those.

I certainly appreciate you continuos efforts to get this resolved!! Most people i know would have given up and lived without it by now.. i'm the type that it's a mystery that i gotta figure out the answer to.

Let me know on the powertrain control module and i'll get on that.

Thanks again Mike!
Jim

Customer: replied 4 years ago.
By the way, another buddy mentioned a Body Control Module... is that a possibility?
Expert:  carhelpguy replied 4 years ago.
Hey Jim, thanks for getting back with me. The powertrain controller is located on the right side of the dash behind the glove box. What you will have to do is lower the glove box and you should see a silver box on the right side with several connectors.

In regards XXXXX XXXXX body control module (BCM). The module on this one really does not control any of the cruise functions and is more of a lighting controller. I have seen this on the newer models though but not on this one.

A hat pin is just a large pin found in a sewing kit used for pinning clothes. Sounds like the scanner is a good one that should be able to tell us alot. Let me know if you can get a hold of it and we can go from there. I love a challenge and I will do everything I can to get to the bottom of this.

Talk to you later.
Customer: replied 4 years ago.
Hey Mike, Ok so the powertrain controller is the same as the ECM? That's what i switched out with that one from Autozone, it was made by Cardone. When it temporarily worked, the cruise still was out.

Is the BCM located underneath the ECM? little black plastic box? So the BCM would have no ties with the cruise at all?

I will see if i can borrow the scanner if i can get in his garage.

Thanks,
Jim
Expert:  carhelpguy replied 4 years ago.
Hey Jim,

Yes, the PCM is the same as the ECM and is the module that you replaced. I often use both acronyms by accident and it can be confusing, I'm sorry. Looking more at the BCM for your vehicle. I think they are only used on luxury model utilities like the Escalade as it is being shown under the center console. The small black box under the ECM, I am not locating it yet, but I think might be the vehicle speed sensor buffer module.
Customer: replied 4 years ago.
Hey Mike,

Ok well i found out that the scanner tool my buddy has only scans for codes and it's not upgraded to do diagnostic work. I'm willing to go rent one or purchase one if i have to. What am i gonna be looking for? I can't swing a couple grand for one, but a few hundred bucks i can justify. If i gotta spend more than that, i'd probably be better off to go to a GM dealer and let them check it for what ever they charge.

Thanks,
Jim
Expert:  carhelpguy replied 4 years ago.
Hey Jim, sorry it has taken so long for me to get back to you the site has had some issues and I have not been able to get into your question. I am not sure if parts stores would have one for rent that would have the capability to read data. The only other scanner I have used other than the GM TECH2 would be a snap-on scan tool which is also expensive. I have seen a few others for about 500 to 600 online but to be worth getting you would have to look at how much you would really use it.

Tell you what. Lets go through the voltage tests first and if necessary then we will see about having a dealer scan the truck's data stream.

Let me know.
Customer: replied 4 years ago.
Hey Mike,

No worries pal, i've been pretty busy as well! I did install a new brake switch yesterday, since it was a cheap part i figured why not. Well it didn't change anything. I talked to another buddy who is also a GM mechanic who just happens to have his Tech II at home with him... he's gonna check it tomorrow for me. I'm assuming that it will test voltages as well? So would it be worth my time to check voltages today or just wait until tomorrow you think?

Thanks,
Jim

BTW Here's my email if the site has any more issues:XXX@XXXXXX.XXX
Expert:  carhelpguy replied 4 years ago.
Hey Jim, GREAT DEAL!!. A TECH2 will help a great deal. It will not tell you voltages however it will have great data to look at. Check the data first and then we can customize our tests to what the data tells us. Let me know what you find.

Especially look at freeze frame/failure records for pending codes as well as any current or history codes. Look at the brake switch and TCC brake switch data in the engine control module as well as monitor the vehicle speed input in the engine control module and lets go from there.
Customer: replied 4 years ago.
Hey Mike,

I'll definitely let you know what we come up with. I'm gonna make sure i show my buddy all the info you just listed out for me.

Thanks for your continuing support!
Jim
Customer: replied 4 years ago.
Hey Mike,
Great news... the cruise is back working again! My buddy put it on his Tech II yesterday and found a 1217 code (FSD response time too slow) on it, that showed up from the last ignition cycle. He noticed that the time that the ECM was showing was way above specs, so he cleared it and we ran it again with the exact same results. A red wire from the FSD is what sends the info to the ECM, so we traced it and found out the wire harness connector was faulty ONLY on the red wire.. go figure! The only way he was able to figure that out was he took a wire connector that he had in his tool box and checked them all individually, when he got to the red, it wouldn't hold the connector. He cut off the red wire connector, put on a new one, plugged it in, and ta-da...the cruise was back on! Amazing... 15 minutes of actual work that took well over a month to figure out...frustrating, but yet rewarding both! I've now got him researching the turbo boost.. when i'm on the expressway it cycles on and off about every 15 seconds. It turns on for 2-3 seconds then back off for 15-30 seconds. I'm not sure if its supposed to do that or not...seems kinda odd. Any thoughts to share on that??

Thanks again for your continued support and help with getting the cruise going again! You hung right in there, and i really appreciate it!
Jim
Expert:  carhelpguy replied 4 years ago.

Good to hear. I thought there may be something that we could not see blocking the cruise. Thats the way it goes with auto repair some days. As for the turbo, that does seem odd. Does the vehicle seem like it is surging when this does this? The only thing that comes to mind as a possible cause is an incorrect reading from the manifold pressure sensor which the engine controller uses to judge how much boost to give. Monitor the pressure reading to see if it is fluctuating incorrectly. Also monitor the vacuum solenoid that controls the turbo dump valve for cutting out and go from there.

 

Good job on the cruise. I am glad to have helped.

Customer: replied 4 years ago.
Thanks Mike, so do i need to hit "Accept Answer" and star a new "thread" about the turbo...or can we just continue this? I want to make sure you're getting paid...that's my biggest concern!


Thanks!
Jim
Expert:  carhelpguy replied 4 years ago.
I am not sure about their policy about the second question about the turbo. You may want to email them and find out exactly. I know that by clicking accept that will for the most part close the question about the cruise and will allow me to be paid but you do still have access to the question.
Customer: replied 4 years ago.
Well I want you to get paid...but I'd like to have your help with the turbo...so I'm not sure how to go about that. What do you think?
Expert:  carhelpguy replied 4 years ago.
Hey Jim, email them and ask them. I believe you can request me on the second question if you post another or they may let you go through this one. I am not sure how they work customers accounts. I am here to help any way that I can and would love to be able to help with the other concern.
Customer: replied 4 years ago.
Sounds good mike, just let me know.

Jim
Expert:  carhelpguy replied 4 years ago.

Hey, Jim. I still have not received any word on this one. To be safe and, if you feel comfortable with it, start another question about the turbo concern and then put something in the question to request me if you would like. I will try and grab it as soon as I can see it.

 

Talk to you later

 

carhelpguy, ASE Certified Tech.
Category: Chevy
Satisfied Customers: 146
Experience: Over 15 years of experience working on GM, Ford, Chrysler, Toyota, and Honda. Diesel and Electrical specialist.
carhelpguy and 6 other Chevy Specialists are ready to help you
Customer: replied 4 years ago.
Sounds fine to me...thank you for all your help!
Jim

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