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01 silverado duramax allison engine code p1781

14K views 9 replies 5 participants last post by  Charlie B 
#1 ·
Hey out there!
My service engine soon light came on, p1781 checked for free by Autozone.
I understand to check connections at the TCM what and where is the TCM??
Also TSB 01-06-04-020 anybody know what to do?
Thanks in advance for any help.:)
mkcanfield
 
#2 ·
don't see that code in my books===charlie
 
#5 ·
is this code just specific to an 2001, because I just looked again through my 2004 service manuals and there is NO code P1781
 
#7 ·
Charlie B
Thanks for your reply, I got the code from autozone free check.
The code means poor or lost communication from the TCM (transmission control module)
I do not know where the TCM is located to check for the connection.
Can you tell me where it is located??
Thanks
mcanfield
 
#10 ·
I would check all the transmission connections also, speed sensor on the transfer case, input shaft sensor close or on the bell housing and the P/N Position switch mounted to the transmission by the shifting linkage. charlie
 
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