I just picked up a new truck equipped with a MP112, along with a 90mm TB and the X-link.
Truck is a 2003, 4.8l, RCSB, 2WD. I bought everything as it sits, so unfortunately I do not too much about it, and this is the first I have ever seen of an X-link. I have done some searches and reading so far finding unfortunately quite a few people having issues with the X-Link and it putting them in REP mode.

Here is what my truck does:

Everything is great at idle, cruising, moderate throttle. At WOT or rolling into WOT, it tosses a P1515 and puts me into REP mode. It does this at different times as well. We were in process of tuning the truck last night thinking this issue was something we could clear up in tuning but no luck. We got the truck to go WOT all through 1st gear, upshift into second, and about 4000 RPM it then shut me down tossing the P1515. Tried again and same thing. Then rolling on starting in 2nd gear, it did the same. Later on that night, tried it in 1st gear and this time it shut me down immediately when I went WOT in 1st gear, so it is not the same result every time.

Curious what I might be able to do to diagnose this X-link, TB, or what. I would like to keep the 90mm TB. Here are some pictures of the X-link and how it is set-up on the truck!

The truck also has randomly thrown a TPS code, I forget the actual code. This happens right at start up, only 2 or 3 times on me. Immediately on start up it will go into REP with that code. Next time it pops up I will record the code and post it up!

Thanks in advance for any assistance!

 

i had this problem twice when tuning trucks. Once on a turbo truck, and the pressurized air would shut the flap closed whilst the tps would be 100% hence the TAC module had an offset from the electronic throttle table

engine>airflow>electronic throttle> desired throttle area

another solution with a non turbo truck was to flash a newer OS in the truck from a newer truck and go to engine>torque management> ETC tps max and 100 everything.

 

This happens to me when the x-link box itself gets really hot to the touch. I bought a can of freeze spray and when I get the code I have to cool the box down then clear the code and it's good. It usually happens when the truck is sitting for a while after driving around in the heat. I haven't come across a better solution yet.

 

I battled this problem for along time. The solution for me was to run the silver blade LS2 throttle body. The LS2 throttle body opens in the opposite direction. I believed the air was forcing the blade closed causing it to go into REP.

What size pulley are you running? It seems as though this problem comes up more with smaller pullies. Has the truck been tuned? A tuner should be able to adjust the air flow tables eliminating this if the pulley isnt too small.

 

Sounds possibly, we are going to try this tonight, thanks!

 

Interesting! It is a 3.2" pulley on the 4.8l, so it should be 10-12 psi I believe. We are in process of tuning it but can only get so far with this issue.

 

Gave it a shot and no bueno, thanks though! Thinking it is something mechanical, not tune

 

I believe when this is happening that air is forcing the blade closed. Try logging actual throttle position and watch it trip into REP. When it happened for me it would show the throttle position changing right before it tripped.

The first thing you need to try is to move the throttle in its full range of motion with key on engine off. It should move without any binding. Another thing to check are the wires right before the X link. Pull on the brown and yellow wires and see if they are broke under the insulation.

 

P1515 sets when actual TP does not equal commanded TP. The TPS signals are good. Check for binding of the throttle blade at any position, an intermittent or weak connection in one of the throttle motor wires (brown, yellow), the blade hitting the stop at WOT, or a weak throttle motor.

See also Throttle Troubleshooting

 

I believe we may be seeing the throttle blade fluttering issue. I pulled the inlet tube off and the gold throttle blade is not getting hung up on anything. I then tested it with the pedal and it opens without any issues.

Black and yellow, as well as all other wires look just fine!

Could the forced air from the mp112 cause the throttle blade to flutter under WOT tripping this mixed signal with actual throttle blade position?