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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8413
Experience:  I am ASE Master Truck Certified.
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I took a 3126 engine from a 2000 gmc with a standard shift

Customer Question

I took a 3126 engine from a 2000 gmc with a standard shift transmission and put it in a 2006 ff 650 in place of a c7 with automatic transmission. My problem is that the transmission is shifting out of first and going into limp mode.Allison transmission dealer hooked it to a computer and says I am not getting a tps reading to the transmission and yancey catapillar says I'm not getting a rpm reading to the transmission. What do I need to do to fix this problem. I used all the sensors from the c7 but I used the computer from the 3126. Both with70 pins. I originally used the c7 computer but it wouldn't fire the injectors. Replaced it with the 3126 computer and it fired right up. Can I put the c7 computer back on it and have it programed to work the injectors in the 3126. HELP
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.

Thanks for asking your question and requesting me. I will try and help you out.

Unfortunately the C7 and 3126 ecms are different. They look the same but are different inside. Also the have very different injectors. I am sorry. I wish they were interchangeable.

Please reply back if you need more help or have more questions. I am happy to assist.

Expert:  Cat Man replied 1 year ago.

Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.