Mopar trailer wiring

[Grasshopper]

Ok. Reaching out to see if anyone has run into this. I have a 2018 Jeep JL. I bought the Mopar aux switches and the Mopar trailer wiring kit. Installed switches no big issue, this was on saturday. Sunday installed the trailer wiring. Went to start Jeep now i have check engine light on. Mopar trailer wiring is Pigtails (plug and play ) for the tail lights, a module, and positive / ground. Checked wiring through firewall didnt see any wires damaged. Codes are P2127 “ throttle / pedal position sensor / switch circuit low and P057d “brake switch out of self - test range. Runs rough (of course with CEL on), no throttle. I cant find anything related to what was done. both kits were Mopar OEM from the dealer. No issues Saturday night after aux switches. Any thoughts would be great.

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[MEHillwalker80]

Two things come to mind since I have done both of these projects. #1 How did you run the + wire from the trailer kit to the Battery? #2 any difficulties getting the Aux wire bundle through the firewall rubber boot under the smaller battery. The reason I am asking is that someone reported breaking some unknown wires when using a sharp ended coat hanger wire through the rubber boot.

 

[Grasshopper]

So i thought of that first. A friend of mine helped me and did that part. I brought the jeep to my work , Toyota dealership, and myself and my shop foreman removed the fuse panel and all the wires blocking the grommet in the firewall. Pulled the main harness out enough to inspect it. Saw no real damage. A few wires had marks on them but not cut or exposed. For Mopar kits they were not easy to get through that grommet. As far as we can tell there was no real damage. It’s puzzling because these are OEM kits and basically plug and play.

 

[MEHillwalker80]

So i thought of that first. A friend of mine helped me and did that part. I brought the jeep to my work , Toyota dealership, and myself and my shop foreman removed the fuse panel and all the wires blocking the grommet in the firewall. Pulled the main harness out enough to inspect it. Saw no real damage. A few wires had marks on them but not cut or exposed. For Mopar kits they were not easy to get through that grommet. As far as we can tell there was no real damage. It’s puzzling because these are OEM kits and basically plug and play.

Here's what I would try if you already haven't: Unplug the switch connectors from the back of the AUX Switch panel, and double check the part where you have to re-pin one connector the big plug in the right kick panel. Re-pinning that to insert that new wire routing was the most difficult part of the install for me. I ended up cutting and splicing the new circuit in. After the install was finished, I used JSCAN to get the Jeep to recognize the new switches. If unplugging brings things back to normal then at least you can begin to reexamine the install procedure. Just an added note: I taught Electronic Trades at Spaulding High School in Rochester from 1980 to 1990 before retiring.

 

[Grasshopper]

I think where it went wrong was the trailer wiring. From what i understand from Jeep is some of the newer ones (with start / stop) need to be enabled at the dealer or it can throw codes. It’s at the dealer now so I’ll let you know what I find out. I did disconnect both kits before resorting to bringing it there. It’s basically in “limp mode” right now. They believe it just needs to be flashed. If thats all it is ill have them reconnect everything and program it so I don’t have to deal with it again. Hopefully By my mistake I can help others.

 

[Trk3263]

Any update on this one? Looking to do both these additions in the near future.

 

[SargeDeputy]

I think where it went wrong was the trailer wiring. From what i understand from Jeep is some of the newer ones (with start / stop) need to be enabled at the dealer or it can throw codes. It’s at the dealer now so I’ll let you know what I find out. I did disconnect both kits before resorting to bringing it there. It’s basically in “limp mode” right now. They believe it just needs to be flashed. If thats all it is ill have them reconnect everything and program it so I don’t have to deal with it again. Hopefully By my mistake I can help others.

Did you ever find out what the issue was?

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