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JCTech, Diesel Mechanic
Category: Heavy Equipment
Satisfied Customers: 387
Experience:  31 years experience as a Diesel Mechanic, 14 years at Cummins, good with electronic control systems
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Heavy Equipment

Power harnesses for my 3406E Cat..boost..resistance..resistors

I'm in the process of... Show More
I'm in the process of making power harnesses for my 3406E Cat. (boost & fuel temp) From the information I've found so far, I've found several different resistance values for the resistors. Does anyone know the proper resistors to use? I'm trying to avoid the "trial and error" method. Thanks for any help! Jim.
Submitted: 7 years ago.
Category: Heavy Equipment
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Satisfied Customers: 14
Experience: 23 Yrs Diesel Engine Mechanic (A.S.E Truck and Bus, Catapiller Engine,14 U.S. Army generator repair)
replied 7 years ago.

Hello, I'm Dale and will try to assist you.

The reason there are several different resistors is because of the specific " ENGINE SPEC'S " that are unique to your engine "AR # " (arraignment #). Turbo size, Injector size, Base horse power rating, Injector timing just to name a few are some of the reasoning behind the different resistors. You will need to check with the local CAT dealer parts department perhaps for a breakdown of he AR # XXXXX an engine diagram for your engine that list the specific size of the resistor.


Hope this helps, and good luck


Customer reply replied 7 years ago.

I'm very familiar with arrangement numbers etc. I've done all my own work on my trucks for the last 30 years. Cat doesn't put resistors in line for their sensors. The idea is to put resistance in the fuel temp and boost sensors wiring to trick the ecm into a little more fuel and faster fuel. These "power harnesses" have been around a long time and can be bought from several aftermarket manufacturers for about 100 bucks each. All they need to know is your ser# XXXXX (5EK is mine) You can make your own for about 10 bucks. I just see too many different resistance values for my motor. You end up with 75 to 100 more hp, way better throttle response, a slight increase in mpg and a little lower egt. Cat must have put in the newest low nox program in it when I went from 475 to 550 hp. Now it won't get out of it's own way - total dog. My 425 b model will run circles around it. Thanks. Jim.

DALE, DIESEL TRUCK MECHANIC replied 7 years ago.

Ok Jim, however intrigued I am about this, I'm not really experienced in experimental harness fabrications. I will opt out and perhaps another expert can assist you.


good luck,


JCTech, Diesel Mechanic
Satisfied Customers: 387
Experience: 31 years experience as a Diesel Mechanic, 14 years at Cummins, good with electronic control systems
replied 7 years ago.


The power harnesses are a bit more complex than you describe, because the engine ECM checks for 0 PSI boost pressure (compared to atmospheric) when the keyswitch is turned on before the engine starts, it also checks other pressure sensors, to validate the 0 PSI.

So simply fitting a resistor to indicate more boost pressure and less fuel pressure will not work, it will log a fault for the non 0 boost pressure sensor, and any other pressure sensors with resistors in the circuit.

The aftermarket power harnesses have a circuit in them to give the correct sensor reading before the engine is running, and the modified reading after the engine is running.


Sorry to be the bearer of bad news, but better to hear it now than find out after several hours of work and a chopped up engine harness.