What to know about ECM swaps on automatic to standard 1995 Jeep Wrangler YJ. - JeepForum.com
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post #1 of 5 Old 07-12-2017, 09:17 AM Thread Starter
Belizejeep
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What to know about ECM swaps on automatic to standard 1995 Jeep Wrangler YJ.

On 1995 Jeep YJ 2.5L with 3 speed automatic it is originally equipped with ECM part #56028833 for an automatic; these are hard to find, especially in Belize. Chrysler discontinued making them. I sourced a 56028842 for same year from http://shipecm.com/index.php?route=p...product_id=583. It’s for a STANDARD Jeep. What you got to know is IT WILL WORK to run the engine but DO NOT COUNT ON IT TO ACTUATE TCC torque converter clutch solenoid. (unless of coarse you get programed to do so) In the standard ECM 5608842 it is programmed to signal the UP SHIFT LIGHT, on Pin # 54 and this will cause erratic shift points in your auto-trans. In the 56028833 this same Pin #54 is programmed to trigger the TCC solenoid at I think a certain speed of 50-60 MPH. It’s like having fourth gear but really just makes a physical connection between torque converter and engine

So the symptoms on the swap are no shift 2nd to 3rd and when it does shift to 3rd, due to the Standard ECM it will feel like it up-shifts and down-shifts. That is exactly what it is doing because the ECM is not keeping the TCC relay grounded, which opens/closes the solenoid, allowing transmission fluid to lock/unlock the TCC torque converter clutch while in 3rd.

Using this information I started to look at the wiring. Pin 54 feeds out to a 20awg Orange with Black strip wire. It leads to Connector C104 (Black) TCC RELAY and is mounted on the firewall right hand side of the battery. The OR/Bk wire is spliced in the terminal 86 in the relay and leads back to the right hand side bulkhead connection on right hand of the master brake cylinder. It routes through and goes to the wire harness on the instrument panels up-shift terminal.

SO if you do not have access to reprogram your ECM or have it sent back for reprogramming. Here is what you can do to work around it. Below is the original wiring and modified version for this modification.

These are the parts you will need.
1 – 12 volt relay similar to what is mounted on the fire wall. See Relay image. Modify it by bridging pin 86 & 30.
1 – 12 volt momentary rocker switch preferably with light to indicate it is on. Similar to this or rocker type momentary switch http://www.ebay.com/itm/TCC-Lock-up-...FY31Gi&vxp=mtr

10 spade connectors male and female ( have some extras if you mess up )
2 packs heat shrink tubing
1 roll electrical tape
1 length of ” wire loom (12 inches will do)
And 18 or 20 awg wire. (you will need 4 for the relay you will install and 2-4 for the switch connection on dash depending on if your switch has a light or not. try to match your wiring if you can) ( I got most of what I needed from a scrap yard but they didn't have any Wranglers so did well with what I got)

Hope this helps anyone having issues with autotrans no shift or shift problems or ECM swap issues.

This modification simply bypasses the ECM with a manual TCC actuator switch. The additional TCC relay acts like a switch that feeds a always closed negative signal to the factory TCC. When I apply the brake TCC circuit is reset/OFF. This is so the engine does not stall when coming to a stop. The circuit is ready until I need to activate it again, by the push of a button ... I no longer have shift issues. I have smooth shifting 1-2-3 and when I press TCC switch on my dash @ 55-60 I get lock-up torque and better fuel mileage on long distance runs.

In a few days I'll do a video that illustrates what I did...Keep Jeepin!

Attached Thumbnails
YJ ECM pinout.jpg   Relay 2-01-01.jpg   yj trans control revised.jpg   Engine Compartment Connection-01.jpg   yj trans control.jpg  

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Last edited by Belizejeep; 07-12-2017 at 04:45 PM.
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post #2 of 5 Old 07-12-2017, 11:14 AM
Jeepsr4me
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excellent info... Could use a short version to explain what you did as all the other stuff just made the post harder to understand for those electrically challenged
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post #3 of 5 Old 07-12-2017, 01:00 PM
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Agreed...well done!
I'm sure this post will be a great help to others that will face this same situation.

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post #4 of 5 Old 07-14-2017, 04:26 PM Thread Starter
Belizejeep
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This is the shortest version I could do. Hope this helps to visualize. Thanks for the likes and comments.
Attached Thumbnails
TCC Relay install engine 1.jpg   TCC Relay install engine 2.jpg   TCC Switch Panel Connect.jpg  

Last edited by Belizejeep; 07-16-2017 at 11:52 AM.
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post #5 of 5 Old 07-28-2017, 03:28 PM Thread Starter
Belizejeep
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Another option for this work around that does not require a dash mount switch. ( unless you want total control of tcc then a dash rocker switch can be wired in tandem with pressure switch )

1. Install a self grounding 50PSI normally open pressure switch at the transmission governor pressure test port. It is located right next to the TCC solenoid cable on the transmission case. ( Use a switch like GM GOVERNOR PRESSURE 50 PSI Part# 44416D or similar, you might want less pressure or more. 40 to 55psi seems to be a good range. Anything less will cause stall or shutter feeling.)

2. Wire the pressure switch to the negative terminal to the existing factory TCC relay. You will only need a second relay if a rocker switch on dash is required.

3. The Result will now be that whenever you drive your Jeep the governor pressure at the pressure switch will control the TCC relay negative ground and thus the TCC solenoid valve on the valve-body inside the transmission. It will lock-up @ the psi rating on switch, so 40psi switch will lock-up TCC @ 40-45mph - 50psi switch will lock-up TCC @ 50-55mph - 55psi switch will lock-up TCC @ 55-60mph

Keep Jeepin!
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