2003 ECU swap issues

Sleddin650

New Member
Joined
Nov 9, 2022
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8
Location
Wisconsin
Hello everyone,
This is my first thread and I want to first start by saying thank you for all of your other posts and explanations. I have learned a lot from reading these posts from this site. That's a major reason I joined.

Now, my problem. I have a 2003 X (Non Rubi) 4.0 auto trans, no SKIM that I swapped in a 2004 Rubicon ECU and SKIM module, key and tumbler. The reason for doing this was my gauge cluster stopped working and after a long time of trouble shooting the ECU was my problem. After the swap everything came back to life and worked fine, but I didn't drive it the day I swapped all this in. I only started it and it ran idled fine and all the gauges worked again. So, I drove it last night and the speedometer goes to max almost immediately while the jeep is only going about 15 -20mph. Everything runs fine and shifts fine, but once the mph hit 95 the rev limiter steps in and I'm stuck doing 20. What would cause this? It ran and shifted fine with the "bad" ecu in there. Could this have something to do with not updating the vin in the new ECU yet? Does it have to match the TCM vin? I have a programmer that will change the VIN I just haven't tried it yet. I wanted to see if there were more experienced people here that might know what I am experiencing.
I have "relearned" the TCM and reset the ECU many times. Let me know your thoughts please. I am going to put in my VIN tonight to see if it changes anything, but I don't have a lot of faith in that being the fix.
Do I need the TCM from the Rubicon I took the ECU and parts out of?

Thanks again!
 
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The speed is read differently with a Rubicon vs. all other models of TJs, the Rubicon does not use a speedometer gear like your X does. I suspect that is the sum of your issues with the speedometer not working properly.
 
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Update: I disconnected the speed sensor at the back of the transmission and now it runs great.....but now I have no speedometer. Anyone have any ideas?
I thought I was clear that your replacement PCM programmed for a Rubicon is not set up for the type of speedometer sensor used in your non-Rubicon X. I'd replace the Rubicon PCM (aka ECM) with one made for your 2003 non-Rubicon X.
 
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@Sleddin650 I can program the pcm for you with 03 software for you. If you are planning on using the skim module from the 04 the vin cannot be changed to the 03 as it will shut it down.

Sorry for the delay in responding. We have a tropical storm blowing by and people are just stupid.
 
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Do you have two threads going on this because I replied yesterday and don't see it.
mrblaine - You replied to a discussion someone else had that I chimed in on. I haven't had time to respond until now. Thank you for your help as well. Jerry was spot on with the Rubicon PCM being the issue. Per your answer I don't want to add a healer or anything else to the trans to compensate for the digital read being off. I'm going to send the unit in to Wranglerfix and have him program it correctly to my 2003 year.

I greatly appreciate everyone's help. As you know these electronic issues get frustrating.
 
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@Sleddin650 I can program the pcm for you with 03 software for you. If you are planning on using the skim module from the 04 the vin cannot be changed to the 03 as it will shut it down.

Sorry for the delay in responding. We have a tropical storm blowing by and people are just stupid.

Wranglerfix - I sent an email on from the "contact us" portion of the website with your name attached. Since i don't have a paid account here I couldn't message you directly. No worries, I'm easy to get a hold of. LOL. I'd like to send it into you for reprogramming. Thanks again, you guys are awesome.
 
Wranglerfix - I sent an email on from the "contact us" portion of the website with your name attached. Since i don't have a paid account here I couldn't message you directly. No worries, I'm easy to get a hold of. LOL. I'd like to send it into you for reprogramming. Thanks again, you guys are awesome.
You can message once you have 20 or 25 posts. We don't allow brand-new accounts to send messages to avoid the members getting spam messages.
 
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Update: I sent the ECU to Mark at Wranglerfix. What I ultimately needed was to have Mark remove the 2004 Rubicon software and flash it with 2003 non-rubicon software with my original VIN. I just got around to reinstalling it.....BAM! Everything is working fantastic! Thank you Mark for such fast work! You were great to work with and I highly recommend anyone needing PCM/ECU repair or programming to work with Mark @ Wranglerfix. I couldn't be happier.

Thanks everyone for assisting me on this repair. Now I can begin tearing the jeep down to restore it!
 
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