2009 Topkick No Communication TCM

Michael Mobile Technician Utah Posted   Latest  
Case Study
Driveability
2009 GMC C4500 Topkick C4C042 6.6L (9 LMM)
No Communication
Tcm

Called out to program a TCM on a Medium Duty GMC Truck. When I got there the technician explained that the truck was in limp mode, He had gone through the wiring and repaired / checked all wires. When connected to scan tool there was no communication to the TCM. The connection to the TCM was single wire GMLAN. In checking for a waveform at the TCM there was none present. I had the technician overlay a new wire from the splice pack on left side of dash to the TCM. There was then a signal but no comm with TCM. They had a used TCM on the shelf. We tried it and it communicated. I attempted to program this TCM with the part number from original. The hardware must have been different as it tripped trouble codes. I advised the shop they needed a new TCM. The question in my mind is did the technician cut the GMLAN wire somehow? The vehicle ran and drove until the TCM failed. The technician was correct in checking the wiring. They did not have any service information. So without a wiring diagram, how would they know what to test? I admire technicians that are willing to dig into things. I wish their employers would invest the resources so that they can be successful. They had been fighting this truck for two weeks. I found the issues in an hour.

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Carl Technician
Ireland
Carl Default
 

Unfortunately Michael this is all too common. Where I work has little to no service info on anything we work on. I work on the Heavy truck side of things where the likes of Alldata do not exist, as far as I am aware anyway. Wiring diagrams were non existent when I started, i've built up a good collection on my own time but feel it is probably not understood as to why or appreciated for that…

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Scott Owner
California
Scott Default
 

Hi Michael, You probably weren't aware of this, but GM SI has some Medium Duty coverage listed. I'm not sure if this is the diagram they/you were looking for - diag​.​net/file/f2hmi6s6p… This can be had for $20 for 3 days of access through ACDelco. acdelcotds​.​com/subscriptions I am with you as it's mind boggling than someone would attempt something like this without…

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Michael Mobile Technician
Utah
Michael Default
 

Thanks Scott, I did find the needed SI. This is how I found which wire to back probe at the TCM and the splice pack. The shop that was working on the truck has no service information and just wing everything.

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Scott Owner
California
Scott Default
 

I was going to reply to your post - diag​.​net/msg/m7hihulvfm… The only thing I can add to any of those posts that were made there, and it distracts from the value of education, would be why do it in the first place? That's a rhetorical question, but really begs an answer... How many people will ever get to the point you're at and can you teach them to think the way that you do?…

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Michael Mobile Technician
Utah
Michael Default
 

Scott, I too am frustrated with the lack of the basics, that is why I want to do something about it. If one has the desire to learn what I do, I am willing to travel anywhere in the continental US and spend time mentoring, teaching, training or whatever you want to call it. It could be one person or a small group. It does not matter if it is a HD Truck, Tractor or Automobile. I can't know the…

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Martin Instructor
British Columbia
Martin Default
   

Hi Mike. Scott has focused on the real issue that many of these shops do not even have technicians with what would qualify as minimum skills levels in the current scheme of things. They might have been able to blunder their way through the 1950s-'60s with nuts 'n' bolt repairs and a bit of "black…ing", but that is a major reason why the general population tends to have little or no respect…

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Scott Owner
California
Scott Default
 

Hi Martin, Thank you for your well thought out reply - one amongst many. The only thing I would add to this - "We also supported these shops by assisting with tool loan and even visiting a shop to lend a hand. These shops were "manned" and managed by real people who we had excellent relationships with. Competition maybe, but the real focus was ensuring the best possible customer experience…

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Martin Instructor
British Columbia
Martin Default
   

Hi Scott. Ah, the perfect world! Still, waking up every day and enjoying going to work and feeling good about having done our best isn't half bad in the big scheme of things! There is something about the community that Scott and Thomas have created here, that brings out the best in those of us who try to make a difference each day. There is no "I" in team. We can all achieve our goals here…

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Scott Owner
California
Scott Default
 

Hi Michael, It's hard to read my intent over the internet and it can be a problem communicating this way. I have the utmost respect for you and what you're trying to do as well. I can pull up some of thoughts that I've posted here regarding the state of affairs with this industry, but the cliff note version is - the vast majority of people here, the various closed Facebook groups, and anyone…

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Michael Mobile Technician
Utah
Michael Default
 

Scott, I did not take offense. I often learn from others perspectives. My defense was more for the growing community of mobile technicians. My experience has been that there are many out there with critical thinking skills. They do not speak up because if everyone is paid roughly the same in the shop, what kind of jobs would you want to do? Diagnostic work that pays straight time at best or…

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Michael Mobile Technician
Utah
Michael Default
 

A quick follow up on this truck. TCM installed, programmed and everything is good to go. -Mike

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Geoff Diagnostician
Hawaii
Geoff Default
 

Even way the heck out here in Maui, both indy shops I have worked for had professional subscription SI. There is really no excuse for an ESO not having it.

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