A limp will set a code(s). Look at current and historical codes. Some codes go from current to history on a key cycle. Then cleared until the next provocation such as heavy throttle up. Many codes are not time/mileage driven. Codes tell of problems the ECM sees, and research can tell you the likely reason why the ECM is holding the engine in limp mode.

Let us know what codes you get.

 

The first code that the dealer read was the injector module, I don't know the code though, but they replaced it and now it is still having the same issue.

We were leaning towards the fuel rail or maybe the fuel filter plug.... Could that cause the same issues?

 

Check the wiring harness by the alternator. This is the first place i would go. Many of these trucks have a bunch of issues that come back to this issue.

 

As stated above, possibly check for the harnass rub, maybe try to do the ice pick trick, when was the last time the fuel filter and tranny spin on filter changed? Since there is consideration with fuel- do you have access to see what the fuel pressures are doing?

 

It disappoints me that the dealer would not tell you the code or codes. Without them anybody is just shootn in the dark.
And many problems with modules are actually the wiring that feeds them. Modules are a tough bunch. More likely wiring.
At least make the dealer guarantee that their diagnoses is the final fix, or they will make it so, without throwing parts at it and charging you for them.

 

I had a problem with my 05 LLY going into a limp mode at random. We new that it was a tranny limp mode though, but it was also throwing a bunch of other weird codes also, like the fuel system. It was narrowed down that one of the wires from the fuse block under the dash and the power distrubution box under the hood was bad. I think it was a pink wire. That was the power supply wire to the TCM. Just throwing that out there. Hope you get it figured out.

 

Inspect the FICM wire harness at the passenger side of the alternator. The harness is tied down with a zip tie, cut the zip tie, open up the plastic loom, carefully check for bare wires. The harness and wires get cut, and sometimes short to ground, by contact with the sharp corner of the FICM bracket. Repair, and insulate with a piece of heater hose.


This is a common problem for the LLY engine. Everyone that has a LLY should check this now!

 

Well we changed the fuel filter and all was good for five miles, then it went back to limp mode. Pulled the code and it was a P0202, #2 injector stuck open. We ran a bunch of power services through it and also looked for loose wires. We ended up finding a loose wire with a metal braket attached to it, the metal bracket was just flopping around directly above #2 injector. We moved the bracket up by the intake and secured it drove 30 miles and no issues.