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Discussion Starter #1
I have an 05 Envoy that I bought with no speedo. I have changed the vss and the stepper motor and still no luck. The only code I get is the cooling fan and the cruise control still works.Is there someplace else I should look or am I looking at a new ECU?
 

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Do you have one of those cheap obd adapters like this....?


On my 2002 Trailblazer the vehicle speed is sent from the PCM over the vehicle data network and I can see and decode that. If you have or can get one of these adapters I can tell you how to get the data needed to at least see if the speed is being broadcast. That can maybe point us in one direction or another.
 

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I sometimes have pairing issues. I have 4 adapters. And they all use the same name and I have to try several attempts get a pairing
 

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Discussion Starter #9
I've got the elm327 And it only partially interfaces. I just got it and there were no instructions, so all I have is a code reader.
 

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Well if you can get the device to pair with your phone, that is step 1.

There won't be any instructions, these things are aimed towards the hobbyists who are used to tinkering with this sort of thing. I am such an individual.

And as far as I have found, no one is doing what I have been fiddling with the last couple weeks, that is capturing and decoding the vehicle communications.


it only partially interfaces
What does this mean? Have you tried any apps that will use the elm327, like Torque, or Dash Command? These will not get what we need and neither will codes but would tell us the elm device is working.

From there what I propose is thus, if you are interested. IF the device pairs with your phone, there is an app that allows one to communicate with the elm327 directly. It doesn't do the work for you, just handles the communication. I can give a set of commands to send that will cause the device to simply show all traffic on the network. The traffic can be saved as a text file.

The app is "serial bluetooth terminal" by Kai Morich. It is on the google playstore.

This text file I can decode and see if the vehicle speed is being sent out by the PCM. If it is being sent by the PCM then the trouble is likely in the cluster. If it is not being sent correctly by the PCM then the trouble should be looked at in that direction (sensor or wiring to PCM)

here is an example of what the raw data stream looks like. The values are all in hexadecimal and need equations to yield the results. The lines with the highlighted '29 10' are speed reports. The middle one equates to 5.297 mph. I have a spreadsheet set up where I can just paste in a data file and the spreadsheet translates the data to the values it represents.

Screenshot_20200718-174817.png
 

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I have an 05 Envoy that I bought with no speedo. I have changed the vss and the stepper motor and still no luck. The only code I get is the cooling fan and the cruise control still works.Is there someplace else I should look or am I looking at a new ECU?
Another thought just came to me...Does it shift OK?? I am thinking if the PCM wasn't getting the vehicle speed from the VSS the transmission shifting woult not be normal.
 

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Discussion Starter #12
I have no idea what the hell any of that code means and I haven't played with it in the last couple days. If you want PM me with your phone number and we can try to figure it out.
 

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I have no idea what the hell any of that code means

:) I haven't yet come across anyone who does!! I only recently figured it out myself. But nevermind that anyway...
I totally didn't think of the potentially easier way of just reading the vehicle speed from the PCM using the Torque Lite app. But you would still need to get that elm327 paired with your phone or tablet or whatever. Does it pair or no? What apps have you tried with it?
 
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