OldSch88L Posted September 12, 2020 Share Posted September 12, 2020 Well, my ECU just fried this afternoon. The question is, are Renix ECUs interchangeable between models? For example, I've got a '88 2.5L manual Comanche, so can I put in the ECU from a manual 2.5L Renix YJ? I opened mine and it seems beyond repair, and anything older and all the XJs at the junkyard are always 4.0L however I do see some 4-cylinder YJs sometimes. Link to comment Share on other sites More sharing options...
Pete M Posted September 12, 2020 Share Posted September 12, 2020 did you check car-part.com or ebay? Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 13, 2020 Share Posted September 13, 2020 Ugh. The catalog can be tedious sometimes. I can look under YJ but yet it still shows all the ECU's for the SJ, YJ, XJ and MJ's in one page. I have never seen a YJ computer for the 2.5L, but if it has the same connection plug for the ECU then it should work in our trucks. That being said, the YJ is an interesting animal for the 2.5L TBI. It uses the same exact setup all the way down to the ECU operations but who knows if the ECU is the same. 87-90 2.5L ECU's can be had, there might be a couple at AMC salvage and even some guys on here who moved away from their 2.5L might still have the ECU. There should even be some reman ECU's out there too. Link to comment Share on other sites More sharing options...
OldSch88L Posted September 13, 2020 Author Share Posted September 13, 2020 26 minutes ago, Pete M said: did you check car-part.com or ebay? Yeah, they want like 300-350$ for a used one on ebay, no thanks!!! But wait a minute! I don't know where you found that carpart.com site, but it says there's one here in Quebec, maybe a 2 hour drive, for 75$ CAD!!!! Thanks a lot for the link!!! Link to comment Share on other sites More sharing options...
JMO413 Posted September 13, 2020 Share Posted September 13, 2020 O'reilly's and AutoZone both show remans available. $120 ish Link to comment Share on other sites More sharing options...
OldSch88L Posted September 13, 2020 Author Share Posted September 13, 2020 3 hours ago, JMO413 said: O'reilly's and AutoZone both show remans available. $120 ish I'm in Canada; I don't have O'reilly's or Autozone over here... I got Napa, CarQuest and Benson. I also checked Rockauto and they don't seem to have any left for 4 cylinders, so I guess I'll go with used parts. Link to comment Share on other sites More sharing options...
OldSch88L Posted September 13, 2020 Author Share Posted September 13, 2020 Just so I don't fry the next one, I want to be sure I am to blame, and not another part of the truck. Everything was fine before, but I was in the process of adjusting the TPS and ISA motor since they were both fully functionning but slightly out of whack. I read on another Jeep forum that you have to have the ISA plunger fully extended, and that you could do it from the diagnostic terminal with pin 11. Did that, adjusted engine speed to about 3500rpm with the ISA extended and unplugged, then shut the engine. Then, via pin 14 on the diagnostic port I fully retracted the plunger. When I started the truck, it wouldn't stay running because the plunger was retracted too much, so I had to give it gas to keep it running, and I started so see smoke coming from the dash at the base of the windshield, in the cluster area. The truck still runs but has no control over the ISA anymore. Bench tested the ISA and it still works, but I noticed that when I fully retract it by bypassing the ECU, it retracts too far and gets jammed. The motor tries to get it moving, but can't. Could this be what cause the ECU to burn a few chips and transistors? Here is the damage, and BTW, even with no power, that thing still stinks up my whole appartment Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 13, 2020 Share Posted September 13, 2020 Absolute carnage of the resistors. Thats impressive. Would you mind posting this link to the adjustment procedure of the ISA. Kinda want to verify the validity of it(with AMC books). On a side note you are one of the few people to really mess up a Renix ECU. If you ever have to adjust the ISA again, just unplug it from the engine harness and let the engine scream with a tach, REM or the dash tach to adjust to 3500 RPM, that's usually how I do it and have no issues afterwards. AMC had a special tool back in the day called the Elb.99 something like that, that would plug directly into the ISA and let you adjust it from there. Course all the tool really was was a way to control it via power, ground and a switch. Could easily be made at home now that i think about it. Never seen the tool in person. Shame there really isn't any old Jeep dealers out here. Link to comment Share on other sites More sharing options...
omega_rugal Posted September 13, 2020 Share Posted September 13, 2020 that was a nasty shortcircuit... can be fixed thought Link to comment Share on other sites More sharing options...
OldSch88L Posted September 13, 2020 Author Share Posted September 13, 2020 10 hours ago, eaglescout526 said: Absolute carnage of the resistors. Thats impressive. Would you mind posting this link to the adjustment procedure of the ISA. Kinda want to verify the validity of it(with AMC books). On a side note you are one of the few people to really mess up a Renix ECU. If you ever have to adjust the ISA again, just unplug it from the engine harness and let the engine scream with a tach, REM or the dash tach to adjust to 3500 RPM, that's usually how I do it and have no issues afterwards. AMC had a special tool back in the day called the Elb.99 something like that, that would plug directly into the ISA and let you adjust it from there. Course all the tool really was was a way to control it via power, ground and a switch. Could easily be made at home now that i think about it. Never seen the tool in person. Shame there really isn't any old Jeep dealers out here. Here's where I found the infamous info; I did just like you said for the adjustement, but I used this site's info to extend and retract the plunger. https://www.jeepforum.com/forum/f12/adjust-idle-speed-actuator-2492081/ Link to comment Share on other sites More sharing options...
OldSch88L Posted September 13, 2020 Author Share Posted September 13, 2020 3 hours ago, omega_rugal said: that was a nasty shortcircuit... can be fixed thought Wow, how would you that? The tracers on the PCB seem burnt, and the components are so melted that I can't see the part numbers anymore. And lastly, where would you go to find and buy these components? Link to comment Share on other sites More sharing options...
omega_rugal Posted September 13, 2020 Share Posted September 13, 2020 26 minutes ago, OldSch88L said: Wow, how would you that? The tracers on the PCB seem burnt, and the components are so melted that I can't see the part numbers anymore. And lastly, where would you go to find and buy these components? - you have to solder wires between the missing traces - i´m sure the part number can be found in the web... or from another ECU - electronics store Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 13, 2020 Share Posted September 13, 2020 Yeah I don’t know if applying 13+ volts to the ISA was good for it. The ECU doesn’t have a built in surge protector. Thinking on it, 12v probably gets to the ECU with all that other electrical in front of it before the 14 charging volts does and the ISA is probably a 12V motor too. So the 13+ volts straight through the ECU to control the ISA probably didn’t help. Which makes sense why the tool existed. Miracle that person didn’t destroy their own ECU. The MS-1700 tool probably would’ve been able to control the ISA or at least read data on it from those ports. Link to comment Share on other sites More sharing options...
OldSch88L Posted September 14, 2020 Author Share Posted September 14, 2020 A little update. I did a bit of cleaning on the circuit board to remove the soot, turns out the damage is not as worse as it seems. All the tracers seem intact, the only real damage is to the ISA motor driver (that upright chip looking thing held on with a black metal clip on that big silver metal part) that blew and melted, and the board under it, which now has a small hole. On the melted chip, I could make out " SCC S452-2", so I went searching on the net. I stumbled on a french Renault Turbo enthusiast's site. The guy looks like an electrical whizkid, rebuilding his dead Fenix ( yes, their Renault ECUs from that era were also made by Bendix, they called it Fenix over there and Renix here) which is built exactly like our Renix ECUs, with the same components. He states that failure is really common for the ISA driver chip for both Fenix and Renix, when the ISA motor gets old and seizes up. He gives an alternative part number, ST Microelectronics TDA2004, which is plentiful and easy to find because it is common in the audio/radio/amp world, and has the same specs as the stock part. So, for sh*ts and giggles, I"ll order one (1.79$ on sale on the site I found) and try fixing it. At the worst, there's a JY 2 hours away from me that has 2 ECUs in stock. I'll keep you updated as I go along. Link to comment Share on other sites More sharing options...
JustEmptyEveryPocket Posted September 14, 2020 Share Posted September 14, 2020 9 hours ago, OldSch88L said: for sh*ts and giggles Good for you! Good luck. Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 14, 2020 Share Posted September 14, 2020 These ECUs were remanufactured after all. God speed and I will await your results. Link to comment Share on other sites More sharing options...
OldSch88L Posted September 21, 2020 Author Share Posted September 21, 2020 Hey guys, I figured I would give an update. I've spent some time online schooling myself about PCB repair. So far, I've removed the faulty chip, cleaned the soot, and scraped/cut away the charred board material, since it becomes conductive apparently. So I am left with what you see in the pictures. My employment insurance came to a stop without warning a few weeks ago, so I'm broke AF. Started a new job tuesday but won't have my first pay until this thursday I think, so I wasn't able to buy the new chip yet, plus I need a better soldering iron, fiberglass resin to rebuild the board as well as sourcing a place that sells copper foil tape to rebuild the tracers and "pads". Since this may take a while and I need my Comanche as soon as possible, I'll put this project on the backburner and buy a used ECU when I can. The good ECU will also be good for reference when rebuilding the tracers. No worries though, I'll pick up and finish this project as soon as I can! I figure it's gonna be a good skillset to devellop. Cheers!!! Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 21, 2020 Share Posted September 21, 2020 I have a spare 2.5L Renix ECU, I can send it to you if you'd like, just so that way you have a working MJ for the time until your ECU is fixed. Link to comment Share on other sites More sharing options...
OldSch88L Posted September 21, 2020 Author Share Posted September 21, 2020 4 minutes ago, eaglescout526 said: I have a spare 2.5L Renix ECU, I can send it to you if you'd like, just so that way you have a working MJ for the time until your ECU is fixed. No worries man, I'm driving my beater Ranger for the time being. I just want my Comanche ASAP because first, I love the friggin' thing, second the heater absolutely cooks and the engine heats up fast whereas the Ranger may be starting to clog the heater core, and third, the clutch in the Jeep is in way better condition that the Ranger, plus the Ranger has an obnoxious exhaust leak at the flex joint that drives me crazy!!!! But I really, really appreciate youur offer; huge thanks to you good sir! Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 21, 2020 Share Posted September 21, 2020 Lol are you sure man? This ECU is just sitting around not getting used and id rather it get used than sit for god who knows how long until i have a need for it. Link to comment Share on other sites More sharing options...
OldSch88L Posted September 21, 2020 Author Share Posted September 21, 2020 22 minutes ago, eaglescout526 said: Lol are you sure man? This ECU is just sitting around not getting used and id rather it get used than sit for god who knows how long until i have a need for it. Yeah, for now at least. With the way things are going, shipping is presently slow... I recently bought from Schardein, it shipped quickly through the US up to the border, and then kinda stalled at the customs. Took like 2 weeks and a half, so if I get paid this week, I'll get a used one shipped from a JY a couple of hours away from me, should be faster. However, if there's a snafu or something, I'll let you know if I need yours. Thanks again!!! Link to comment Share on other sites More sharing options...
eaglescout526 Posted September 21, 2020 Share Posted September 21, 2020 Damn. Well let me know. Link to comment Share on other sites More sharing options...
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