NEED HELP BCM not working with engine transplant

[Heysoze]

I made this account just so I can talk to you. I'm struggling with a electrical problem on my 06 Trailblazer. If possible can you givs me a call or shout.




Too bad we don't have any CAD Geniuses around who could come up with a solution... ;>)

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[mrrsm]

Welcome to GMT Nation... And Thanks for Joining....

The Best "On Topic" Thoroughly Thrashed Out Thread that I can think of that will offer you some Solid, Sound advice on How to Diagnose what looks like a Class 2 Network Problem with your Vehicle... is THIS One:

SOLVED! - No Start, Multiple U1000 codes, Class 2 Serial Communication Problem

2005 Chevy Trailblazer LT, 2-Door, 4WD, I6 4.2L engine Won't start or turn over. No starter signal at starter relay but when jump relay will turn over but not start. No check engine light. All instrument light on when first to key on the go out except battery & gauge warning light stay on...

gmtnation.com

This is a very densely packed Thread and I recommend that you Download, Save and Frequently Watch Will Robinson's (from Robinson's Auto) Video in the Linked Thread on How to Diagnose GM Vehicle Networks that show the very same symptoms you are having with the issue of trying to support TWO PCMs being on the SAME Network.

It is very likely that the Single Wire Class 2 Network is experiencing something like having these two ECMs "Arguing with One Another" in a way that either One or the Other will have to be Removed in order to get ALL of the Stock Modules to be able to communicate again. The central idea with these systems requires following these suggestions;

(1) Only Change ONE Thing-Connection-Parameter or Variable in the System at a time.

(2) Use the Proper Tools to get to the Root of these issues. Tech 2 PICO- or Hantek Scope, Etc. (EDIT: as per @Mooseman and @TJBaker57 get the ELM Unit. THIS one has Top Ratings from 20,000 + Buyers on Amazon:

https://www.amazon.com/dp/B005NLQAHS/?tag=gmtnation-20

(3) Take the System(S) Down to their Essence and WORK BACKWARDS TO ISOLATE THE PROBLEM.

(4) Do some research on similar Dual Network Set Ups that show the way to Isolate one PCM-ECM from the other WITH ONE OF THE CLASS 2 NETWORKS HAVING AN ISOLATED, SELF CONTAINED WIRING SYSTEM (Engine and Transmission Management... for example.)

(5) Class 2 Networks WITH CAN Bus capability or Later Model "High-Low" Network Designs may NOT be compatible with the portion of Networks that are STRICTLY designed for a Single Wire Topology.

(6) Make a Folder and collect EVERYTHING Technical there so you can read the various Product PDFs and seek out these possible Networking Irregularities.

(7) Class 2 Networks do NOT operate on the Old UART 0-5 Volts DC Protocols. They work in the "On-Off" Ranges of 0-7 Volts DC. Check your Installation Manual on BOTH PCMs for the Specs differences between the two PCMs and seek to find any such communications discrepancies.

(8) THIS suggestion should have been made first: Start a Brand New Thread under the Technical category for the Year Make and Model of your GM or GMC Vehicle. The Mods will move it to the right place if necessary.

Hope this is at least a starting point for you...

Welcome Home, Brother... :>)

 

[Mooseman]

Moved to its own thread since it wasn't related to the one you posted in.

Strange that some functions work and some don't. Do you have a scan tool that is able to scan other than P powertrain codes? More specifically, you need one that can scan B body codes. An ELM327 OBD Bluetooth adapter with the Car Gauge Pro app (Android) can scan all codes and is a relatively cheap setup.

Almost sounds like an ignition switch issue with some power not getting to the BCM. There are a number of YouTube videos that show how to check that as well as schematics to guide you.

 

[TJBaker57]

Do you have an elm327 clone obd adapter? Are you willing to record the class 2 data stream for analysis? I can assist with instructions on how to do that and we can see what is happening as far as network traffic.

 

[Heysoze]

Sorry for being so late. I took everything apart and pit it back together it was possibly a bad ground all is well (Kind of) I'll keep everyone updated.

Moved to its own thread since it wasn't related to the one you posted in.

Strange that some functions work and some don't. Do you have a scan tool that is able to scan other than P powertrain codes? More specifically, you need one that can scan B body codes. An ELM327 OBD Bluetooth adapter with the Car Gauge Pro app (Android) can scan all codes and is a relatively cheap setup.

Almost sounds like an ignition switch issue with some power not getting to the BCM. There are a number of YouTube videos that show how to check that as well as schematics to guide you.

 

[Heysoze]

I Have this but don't know how to use it to save my life lol

Do you have an elm327 clone obd adapter? Are you willing to record the class 2 data stream for analysis? I can assist with instructions on how to do that and we can see what is happening as far as network traffic.

 

[Heysoze]

Welcome to GMT Nation... And Thanks for Joining....

The Best "On Topic" Thoroughly Thrashed Out Thread that I can think of that will offer you some Solid, Sound advice on How to Diagnose what looks like a Class 2 Network Problem with your Vehicle... is THIS One:

SOLVED! - No Start, Multiple U1000 codes, Class 2 Serial Communication Problem

2005 Chevy Trailblazer LT, 2-Door, 4WD, I6 4.2L engine Won't start or turn over. No starter signal at starter relay but when jump relay will turn over but not start. No check engine light. All instrument light on when first to key on the go out except battery & gauge warning light stay on...

gmtnation.com

This is a very densely packed Thread and I recommend that you Download, Save and Frequently Watch Will Robinson's (from Robinson's Auto) Video in the Linked Thread on How to Diagnose GM Vehicle Networks that show the very same symptoms you are having with the issue of trying to support TWO PCMs being on the SAME Network.

It is very likely that the Single Wire Class 2 Network is experiencing something like having these two ECMs "Arguing with One Another" in a way that either One or the Other will have to be Removed in order to get ALL of the Stock Modules to be able to communicate again. The central idea with these systems requires following these suggestions;

(1) Only Change ONE Thing-Connection-Parameter or Variable in the System at a time.

(2) Use the Proper Tools to get to the Root of these issues. Tech 2 PICO- or Hantek Scope, Etc. (EDIT: as per @Mooseman and @TJBaker57 get the ELM Unit. THIS one has Top Ratings from 20,000 + Buyers on Amazon:

https://www.amazon.com/dp/B005NLQAHS/?tag=gmtnation-20

View attachment 98366

(3) Take the System(S) Down to their Essence and WORK BACKWARDS TO ISOLATE THE PROBLEM.

(4) Do some research on similar Dual Network Set Ups that show the way to Isolate one PCM-ECM from the other WITH ONE OF THE CLASS 2 NETWORKS HAVING AN ISOLATED, SELF CONTAINED WIRING SYSTEM (Engine and Transmission Management... for example.)

(5) Class 2 Networks WITH CAN Bus capability or Later Model "High-Low" Network Designs may NOT be compatible with the portion of Networks that are STRICTLY designed for a Single Wire Topology.

(6) Make a Folder and collect EVERYTHING Technical there so you can read the various Product PDFs and seek out these possible Networking Irregularities.

(7) Class 2 Networks do NOT operate on the Old UART 0-5 Volts DC Protocols. They work in the "On-Off" Ranges of 0-7 Volts DC. Check your Installation Manual on BOTH PCMs for the Specs differences between the two PCMs and seek to find any such communications discrepancies.

(8) THIS suggestion should have been made first: Start a Brand New Thread under the Technical category for the Year Make and Model of your GM or GMC Vehicle. The Mods will move it to the right place if necessary.

Hope this is at least a starting point for you...

Welcome Home, Brother... :>)

Reading through it now. I need to pull this website up on my laptop it's a bit to much to read via mobile.

 

[Mooseman]

Forget the ELM327, you have "la crème de la crème" of scan tools for these trucks. Just play around with it, you'll get the hang of it. We have a whole section that talks about it.

Tech 2

This is for Tech 2 discussions and to learn to better use the tools

gmtnation.com

 

[mrrsm]

Forgot to add in THIS helpful and instructive TECH2PATHS.pdf file for the OP or for anyone else lucky enough to own a Tech 2 ...and not know that they are holding "The Keys to GM Kingdom" in their hands ...at least up to around the Year 2013: