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4L80E error code 73 - trans light always on

RF5

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well, if that’s the case, I’d have purchased a 3spd truck as it’s mostly all mechanical, the A2’s on up need a higher level of maint depending on model and component failure, that equals parts availability.
My EU customers prefer the older 3 speed trucks
In fact I previously owned a M998 with 3 speed, but I sold it to imported the M1097A2, much better in conditions and with very low mileage (3K) than the M998. The M1097A2 runs much better the M998 and the 4L80E is one of responsible for a smoother ride. But, in the other hand, as you’ve mentioned, it has a more complicated maintenance.
 

REF

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Do you have any friends with an early 90's GM truck?
That TCM is a GM#16147609. If you can find an early 90's GM pickup with a 4 speed automatic you can swap TCM's with them to ensure your TCM is completely repaired.
 

RF5

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Do you have any friends with an early 90's GM truck?
That TCM is a GM#16147609. If you can find an early 90's GM pickup with a 4 speed automatic you can swap TCM's with them to ensure your TCM is completely repaired.
I will try, thanks for the tip. But these GM trucks here in Brazil are so rare as the Humvees.
 

REF

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I can't Verify that number, My book shows, on page 50-1 Item #6 16196390. This unit uses an EPROM that is removable through a door on the top of the TCM. You can replace the Eprom to change shift points for non turbo or turbo trucks. I understand there is a newer TCM that does not use an EPROM but I am not familiar with it. you can search the number and pictures should allow you to see if we are talking about the same thing.
Early 90' GM Part Number 16147609
Late 90's part number and the one that showes up in my manual- GM part number 16196390
Both use EPROMS .
 

RF5

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Sorry, I didn’t explain very well. What I asked is about the Humvee TCM. My M1097A2 came with a TCM-2100BB, but searching in the internet it shows (in most of sites) this TCM is used for 6.5L turbo Humvees. If that is correct, my Humvee is using a wrong model and then I should replace by a TCM-2100AA version.
 

REF

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That Part number TCM-2100AA or BB doesn't show up in my parts manual, You can download the parts manuals on this sight for free you are looking for manual # 9-2320-387-24P. on page 0057-00-1 it shows a nsn number and 16196390.
 

RF5

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That Part number TCM-2100AA or BB doesn't show up in my parts manual, You can download the parts manuals on this sight for free you are looking for manual # 9-2320-387-24P. on page 0057-00-1 it shows a nsn number and 16196390.
Ok, done, thanks! Will see if it is possible to replace the EPROM.
 

Coug

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Only difference between those part numbers is the shift points.

According to the below list found on a different site, the -BB is for a non-turbo truck.


2100-AA: turbo first generation
2100-AB: turbo second generation
2100-AC: turbo latest generation

2100-BA: N/A first generation
2100-BB: N/A second generation
2100-BC: N/A latest generation

 

RF5

New member
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Brazil
Only difference between those part numbers is the shift points.

According to the below list found on a different site, the -BB is for a non-turbo truck.


2100-AA: turbo first generation
2100-AB: turbo second generation
2100-AC: turbo latest generation

2100-BA: N/A first generation
2100-BB: N/A second generation
2100-BC: N/A latest generation

Thanks for the valuable info! But now I’m confused… Talking with Hummer Parts Guys, they said the TCM-2100BB is for turbo trucks and the 2100AA is for N/A trucks. In their website the TCM in stock shows these information, which are the opposite of the one you posted above.
So now, which one is the correct? Below is one of the links showing a 2100AA. In the product info, it says that it fits N/A trucks.

 

Coug

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Thanks for the valuable info! But now I’m confused… Talking with Hummer Parts Guys, they said the TCM-2100BB is for turbo trucks and the 2100AA is for N/A trucks. In their website the TCM in stock shows these information, which are the opposite of the one you posted above.
So now, which one is the correct? Below is one of the links showing a 2100AA. In the product info, it says that it fits N/A trucks.

The one you linked shows a -BC ending and says for non-turbo trucks.
 

Retiredwarhorses

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Y’all getting way to deep into the weeds here, any of the hmmwv TCM’s work on any of the TCM equipped trucks, when they retired out the old version and PCS filled the void, it’s a throw away part, no EPROM changes to change the shift points, that’s it…shift point changes were
done because of the heavier armored trucks,generally it’s the 1st to 2nd gear delay in shifting….irrespective of the TCM you are using? The truck should shift….i have and find NA chipsets in many many M1151’s and 65’s and they run and drive perfectly, others have the later PCS, and again in that variation mixed with NA and Turbo versions, I personally like the CZSW chipset….its the most predominant chipset I’ve found in hundreds of TCM’s and shifts very nicely throughout all the ranges
 

RF5

New member
27
3
3
Location
Brazil
Y’all getting way to deep into the weeds here, any of the hmmwv TCM’s work on any of the TCM equipped trucks, when they retired out the old version and PCS filled the void, it’s a throw away part, no EPROM changes to change the shift points, that’s it…shift point changes were
done because of the heavier armored trucks,generally it’s the 1st to 2nd gear delay in shifting….irrespective of the TCM you are using? The truck should shift….i have and find NA chipsets in many many M1151’s and 65’s and they run and drive perfectly, others have the later PCS, and again in that variation mixed with NA and Turbo versions, I personally like the CZSW chipset….its the most predominant chipset I’ve found in hundreds of TCM’s and shifts very nicely throughout all the ranges
Mine is shifting perfectly too with the 2100BB. The only issue is the trans light always on. The only error code is 73 (PCS circuit). I’ve tested almost all the suggestions here, including replacement of PCS, internal 4L80E harness, CPK and continuity check of the wires. None of them solve the issue and the trans light keeps always on and gears shifting smoothly and nice. I also repaired the TCM replacing the drive chip, as the board was a little dark, indicating some hot IMO.
I really don’t know what to do now after all of these parts replacement and procedures done following the maintenance manuals.
 

Mogman

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Mine is shifting perfectly too with the 2100BB. The only issue is the trans light always on. The only error code is 73 (PCS circuit). I’ve tested almost all the suggestions here, including replacement of PCS, internal 4L80E harness, CPK and continuity check of the wires. None of them solve the issue and the trans light keeps always on and gears shifting smoothly and nice. I also repaired the TCM replacing the drive chip, as the board was a little dark, indicating some hot IMO.
I really don’t know what to do now after all of these parts replacement and procedures done following the maintenance manuals.
Just curios Is the light on with the TCM unplugged?
If you have a code 73 then it is normal for the light to be on, if the PCS ohms out normal at the TCM plug then changing the chip did not fix the TCM
 

RF5

New member
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Location
Brazil
Just curios Is the light on with the TCM unplugged?
If you have a code 73 then it is normal for the light to be on, if the PCS ohms out normal at the TCM plug then changing the chip did not fix the TCM
Unplugged the TCM and the trans light went off, as expected.
 

Mogman

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Unplugged the TCM and the trans light went off, as expected.
Then it is definitely coming from the TCM, as I said as long as you have a 73 code that light should be on, since you are doing board level repair I would lok at any electrolytic or tantalum capacitors on the board, I would try to follow the circuit board traces going to the pins associated with the PCS and just shotgun any caps along the way.
 

Mogman

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I did not see, you have the correct reading (ohms) at the associated pins (C15-D16) around 3-5 ohms at the PCS, yes?
 
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