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A50 TCM in LBZ?


New Member
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North Bergen
I have a friend who has accidentally fried his TCM by touching a booster cable to the housing, and he purchased a new one at the local dealership. He was told it did not need a flash. The truck is a 2006 and throws ABS/Brake lights, has no gear indicator, speedometer, and will not shift from 1st gear. My V2 throws p0602 which is the TCM is not programmed. The TCM that was sold to him is an A50, instead of an A40, and is not flash-able. Is a Tech2 able to flash this controller with an LBZ OS? I thought I had read that the A40 ran on class 2 and the A50 on GMLAN low speed, and is therefore incompatible.


Staff member
Lead Moderator
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Ok, had to do some digging on this one because this has proven to be a tricky one of late. I'm assuming this is a pickup and not an medium duty kodiak. For an A40 replacement you need either a used A40, A46, or a T14A. An A50 or T14 is for 09-15 LMM & LML and will not work for an LBZ. Now is where it gets tricky. If you find a used or new old stock A40, it can be flashed with a tech2 using tis2000 or tis2web in pass through. If you get an A46 it should be able to be flashed with a tech2 in pass through using tis2web. If you get a T14A, you will most likely need an MDI to flash it using tis2web and GM's SPS as the tech2 and tis2web has bricked several trying to flash them. If you have a medium duty Kodiak, you need to find an Allison dealer to get it flashed for anything other than an A40 from what I could find. It has to do with the boot software changes in each model TCM and how GM does not flash the boot software, only the operating system and calibration. If he still has the burnt one, tell him to try adding a case ground to it. Several have soldered a 10 gauge ground wire to the housing and ran them for years that way.