3126 cat goes into "engine protect" mode and does 45 mph??

If this is supposed to be "cute"...You'll get "cute" answers too.

Pull the ECM plugs and clean the connection

If its "Too hard" (Yes, I heard drivers that own small cat Motors that are too Lazy to get to the Plug because they have to get dirty because its Hard to get to)... Then to the Shop you go.

 

They may need to talk to the ECM to tell it the sensors are new.

 

Hey Rolls. If you have a truck with a 3126, then my bet is that it is old enough for the engine harness to be bad. Besides Volvo, I replace more Cat harnesses than any other. 3126 being the most problematic. Good luck.

 

Im going to say this. You need a computer to talk to your engine computer to discover the code and it's meaning. Once you have that you should also understand what it will take in parts to make code go away.

Throwing parts at the truck adds up fast. Ive done that too. Bites me every time. I just ship it to the shop, let the computers decide whati's what and then mechainic fixes it. There is too much money riding on the #### to be cheap throwing parts at it outside of a shop.

There is a reason I like older non computer truck and cars. You can fix it. Today? Head to the shop and put together your money. At least they should fix the #### thing, put a warrantry on it and should it throw a code again, they can fix it on their dime. No shop wants to see you back again for the same problem.

 

It may come across as a stupid question but it has to be asked. You did check your coolant level, right?

 

You can buy a generic scanner to pull the codes for DD or a Cat, Cummins and Volvo require factory software though. We have a few generic serial port setups in our mobile repair trucks, use factory programs on the main shop laptops.