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Thread: LM/PM to SMEC conversion w/o rewiring the car

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    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    LM/PM to SMEC conversion w/o rewiring the car

    I did a write up for the Knowledge Center but it's been three weeks or so and hasn't been published so I'm putting it here.

    Why Even Do This?
    I did this because I swapped an early Turbo 1 (‘84-’87 suck through throttle body) engine to a later Turbo 1 (‘88 & up blow through throttle body) engine in an ‘85 Chrysler Town & Country wagon. The early turbo 1 (T-I) engine used a two wire Idle Air Control (IAC) motor and the later T-I engine uses a four wire. I was going to just run a idle up solenoid for the a/c but it idled like crap when it was cold. It was getting to much fuel. I was going to modify the calibration but there is almost zero support for the ‘85 LM. I wasn’t going to design a timer and idle up solenoid for when it was cold so I went this route. I could have looked for an ‘88-’89 K-car with a turbo engine to get the wiring harness, but I said to myself when we got this car that I wasn’t going to rewire the car for a SMEC. Building adaptor harnesses is another story. Besides, these cars are drying up in the junk yards and I could be waiting awhile before I found one. The build log for this car can be found here: http://www.turbo-mopar.com/forums/sh...ad.php?t=40225

    Chrysler Computer History.
    To help those that don’t know I’m going to start from the beginning. From ‘84 to ‘87 Chrysler used two computers for powertrain management. The Logic Module (LM) is located inside and you could consider it the brains and the Power Module (PM) is located under the hood and could be considered the brawn. That’s why the intake air is routed through the PM to keep it cool. In fires the coil, the injectors and contains the voltage regulator.

    A SMEC (Single Module Engine Controller) used in ‘88 and ‘89 combines the LM and the PM into one and places it under the hood. You can open up the SMEC box and remove the two different modules (which you’ll have to do). In ‘90 Chrysler went to a SBEC (Single Board Engine Controller). This write-up only refers to the SMEC.

    What Needs To Be Done.
    I built an adaptor harness to convert the two plugs of the ‘85 LM to the one ‘88 LM. I also had to build a harness to convert the two plugs of the ‘85 PM to the one ‘88 PM plug. I had to add an Auto Shut Down (ASD) relay because in the ‘85 PM the ASD relay was built into the PM. I couldn’t use the ‘85 PM because the injector signal that the ‘85 LM sends to the ‘85 PM is a 10 volt square pattern. The ‘88 LM sends a 5 volt injector signal to the ‘88 PM. The ‘85 PM would not fire the injectors with the ‘88 LM. I also had to switch the thin body ‘85 distributor to the wide body ‘88 distributor.

    Chrysler Wiring Schematics Explained.
    Chrysler does a couple of things in their Wiring Schematics (WS) that made this really simple to build and trouble shoot. In a Chrysler WS each wire is labeled in two parts: 1st is the circuit number, 2nd is the size and color of the wire. I will only be using the circuit number and the wire color. Between ‘85 and ‘88 the circuit numbers and colors didn’t vary much. This explanation is going to come in handy for those that was to convert an ‘84, ‘86, or ‘87 to a SMEC. I won’t be covering that because I didn’t convert those and there may be some variances that YOU’LL need to figure out. But as long as you match up the wire color and/or the circuit number you should be all set.

    In the WS for the SMEC and LM/PM, pins have two part numbers. The first number refers to LM or PM. The second number is the circuit pin. For the SMEC if the first number is a “1” it refers to the LM portion of the SMEC. A “2” refers to the PM portion of the SMEC. For the LM/PM it’s a little different. You need to know which one your dealing with, LM or PM. The first number for the LM if it’s a “1” refers to the RED plug, if it’s a “2” refers to the BLUE plug. When dealing with the PM, if it’s a “1” refers to the 10 WAY connector. If it’s a “2” refers to the 12 WAY connector.

    Connectors I unsoldered out of a junk yard LM. I got them out of an '87 that's why the colors don't match.

    Trimmed and ready to solder.


    I took the wires out to match the colors to the appropriate pins. You don't have to do this, it just makes it easier.



    Adaptor harness done. With map sensor plug and diagnostic connector.


    These are "bullet" connectors I used to plug into the cars PM connectors. I had to squish them down to fit. The normal one is on the left.



    PM adaptor harness done.


    With ASD relay.


    SMEC PM with LM removed


    Installed.




    Kind of installed. Almost like it belongs.


    I didn't include a picture of the pin out for the SMEC because the pins are numbered on the back of the plug.





    The following are special instructions that go with the PDF file that's attached. They're numbered in the PDF file so you'll be able to match them up.

    SPECIAL INSTRUCTIONS # 1: You need to run a wire from the positive terminal on the coil to pin #10 on the SMEC connector. I choose this spot because it’s closest to the SMEC location.

    SPECIAL INSTRUCTIONS # 2: These are the two extra wires that run the IAC on the later T-I that the early T-I doesn’t use. You will have to run new wires from the IAC through the firewall to the LM of the SMEC.

    SPECIAL INSTRUCTIONS # 3: These are for the cruise control. I haven’t wired these up yet as it wasn’t a priority to get this on the road. Update to come.

    SPECIAL INSTRUCTIONS # 4: This wire your going to have to connect to a map sensor. This one goes to MAP sensor signal. Map sensor 5 volt referance goes to SMEC pin 13. Sensor ground goes to ground.

    * SPECIAL NOTE: JI for ASD relay goes to both J1 and J11 on the ‘85 PM connectors. K14 goes to the ASD relay, ‘85 PM connector, and ‘88 PM connector.

    Battery temp sensor is not used because it is built into the ‘88 LM.

    A.J.
    Attached Files Attached Files

  2. #2
    turbo addict
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    well if you can find a 88 turbo new yorker harness then it's plug and play into the 85's bulkhead connector. Also far less wiring to just convert to 87 T2 electronics that support your 4 wire AIS motor and has aftermarket programming support. Don't get that chip wet on the LM board.

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    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    Quote Originally Posted by GLHNSLHT2 View Post
    well if you can find a 88 turbo new yorker harness then it's plug and play into the 85's bulkhead connector. Also far less wiring to just convert to 87 T2 electronics that support your 4 wire AIS motor and has aftermarket programming support. Don't get that chip wet on the LM board.
    IF I can find an '88 turbo New Yorker and IF I can find an '87 T-II LM. I needed to get this car running and through emissions. I didn't have time to search junk yards. This was the cheapest and fastest way to get it done. And it runs great.

    A.J.

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    Buy my stuff!!!!!!!!!!! :O) Turbo Mopar Vendor turbovanman²'s Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    Nice work,
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
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    turbo addict
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    so why is this not in the kc? this is an awesome write up!

  6. #6
    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    Quote Originally Posted by roachjuice View Post
    so why is this not in the kc? this is an awesome write up!
    I wrote an article for the KC. I accidentally put it in the "Turbo Mopar" section, instead of the "Electrical" section. It's still awaiting approval. I wrote that one about three weeks before the date on this article. I got tired of waiting for people to witness my awesomely awesome awesomeness.

    A.J.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    sorry AJ, i never saw this thread till now.

    I do remember looking at the article to approve it but the table was such a cluster in the article that i couldnt possibly approve it until it was cleaned up cause it didnt make sense.

    now, that PDF in this thread is the same thing as the table data in the article? if so, ill attach the pdf to the article and delete the data in the middle of the article.

    Brian

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    Garrett booster
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    I'm with u Mr. awesomeness.Truely awesome.errol

  9. #9
    boostaholic
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    Very impressive, AJ. You make it look so easy!
    Pete Faggella 03 PT Cruiser, 2.4L N/A 5 speed. Daily driver. All stock with baby moon wheels. 85 LeBaron 2.2TBI auto. Hoped I'd see a difference with bumped compression, but I didn't. Still slow. "Life should not be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!'"

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    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    Quote Originally Posted by Big_P View Post
    Very impressive, AJ. You make it look so easy!
    It only looks easy because your viewing the end result. You weren't there after I wired up the LM portion of the SMEC but not the PM (leaving the '85 PM in) and not knowing why it won't run. It's a good thing I had a lab scope (Snap-on Vantage Pro) to determine that the injector driver signal from the LM to the PM is different from '88 to '85. Also if I didn't build adaptor harnesses I wouldn't have been able to switch back and forth '88 to '85 LM's to find the problem.

    A.J.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    im in the process of doing this to my reliant.

    a few changes though.... i have 87 wiring in my 88 reliant that is originally T1 converted to T2. so the pins that are changed from 85-86 to 87 i have to adapt. i printed out the PDF and scribbled my changes onto it for 87. im wiring up the speed control too.

    im got a bad PM (thanks Gary!) and am hacking the connectors off the board. they didnt make it easy though... the back side of the PM connector pins are basically rivets soldered to the board. im cutting the board apart with a dremel.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

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    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    I ended up ditching the '85 harness and adaptor harness' and installed an '89 Lebaron conv harness. There was a problem with my '85 harness. I had to pull the trans and it ran better afterwards but eventually went back to running like crap. Disturbing the harness during the trans work made me realize it. After separating the body and engine harness' in my van so I could install Mega Squirt gave me the way I'd do it in my wagon. I separated the body and engine harness in the wagon, ditched the engine harness and did the same for the Lebaron harness but ditched the body stuff. Then I laid and routed the Lebaron engine only harness in the wagon and spliced it into the bulkhead connector and fusible links. It runs so much better and I enjoy driving it now.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    my harness in my Reliant is in pretty good shape. I also have an 89 Caravan turbo harness that I could use as well if this doesn't work out. the Caravan harness has 2 pins in the firewall connector different then my Reliant harness. I used one once to put a 92 3 liter in a different 88 Reliant using a 90 3 liter Caravan harness
    Last edited by Aries_Turbo; 07-05-2016 at 01:14 PM.

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

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    Supporting Member II Turbo Mopar Contributor
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    Re: LM/PM to SMEC conversion w/o rewiring the car

    You ARE awesome, AJ.
    Thanks for writing it up.
    John Laing

    "The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: MPSciLink

    I MERGED THESE POSTS FROM HERE ON DOWN FROM THE MPSCILINK THREAD CAUSE I CAUSED A MAJOR DERAIL OVER THERE TALKING ABOUT LM TO SMEC CONVERSIONS

    I CHOSE THIS THREAD CAUSE I REFERENCED IT AND CAUSE IT IS GOOD INFO PERTAINING TO THE DISCUSSION.

    Brian


    Quote Originally Posted by wheming View Post
    I'm glad we could help convince you!

    The smec is probably the most supported platform, and as described might be the best overall from all aspects. The sbec's seem described as loaded with too much bloat code.
    And as far as this device goes has had most of the in-service testing.
    ive wanted to do it for a while and i have a 60 way and smec power connector from a 89 harness and spare logic module connectors to make adapters but i dont really want more 30 year old connections so im gonna cut my 87 harness and attach the 60 way where the logic module went and the SMEC power board connector where the PM went and separate the boards. i already have a sci connector in the passenger compartment and having the SMEC logic board in the car will make things easier anyway.

    lots of cutting and splicing here we come.

    Brian
    Last edited by Aries_Turbo; 09-29-2017 at 07:09 PM.

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

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    Re: MPSciLink

    Quote Originally Posted by Aries_Turbo View Post
    ive wanted to do it for a while and i have a 60 way and smec power connector from a 89 harness and spare logic module connectors to make adapters but i dont really want more 30 year old connections so im gonna cut my 87 harness and attach the 60 way where the logic module went and the SMEC power board connector where the PM went and separate the boards. i already have a sci connector in the passenger compartment and having the SMEC logic board in the car will make things easier anyway.

    lots of cutting and splicing here we come.

    Brian
    Gary D suggested to me to take apart the SMEC and place the ECU part in place of the LM and the power section in place of the Power Module.
    I was considering this as a first pass
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: MPSciLink

    Quote Originally Posted by chromguy View Post
    Gary D suggested to me to take apart the SMEC and place the ECU part in place of the LM and the power section in place of the Power Module.
    I was considering this as a first pass
    That's what he did with his reliant years ago and what I plan to do.

    Brian

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  18. #18
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    Re: MPSciLink

    Quote Originally Posted by Aries_Turbo View Post
    That's what he did with his reliant years ago and what I plan to do.

    Brian

    Brian
    I have a socketed smec. So you just need smec connectors then at that point?

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    Re: MPSciLink

    Quote Originally Posted by thedon809 View Post
    I have a socketed smec. So you just need smec connectors then at that point?
    More or less.. A.J.'s smec conversion guide PDF helps too. Though there is one circuit I'm a little unsure of for the power module connections. A.J. connects the black with white power ground to a black with blue stripe sensors ground wire which I'm not sure is correct. When I lay mine out, I'll see if that is ok or if I have to add a wire to get from where the power module goes over to something else in the power ground circuit like the fuel rail ground.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  20. #20
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    Re: MPSciLink

    Quote Originally Posted by Aries_Turbo View Post
    More or less.. A.J.'s smec conversion guide PDF helps too. Though there is one circuit I'm a little unsure of for the power module connections. A.J. connects the black with white power ground to a black with blue stripe sensors ground wire which I'm not sure is correct. When I lay mine out, I'll see if that is ok or if I have to add a wire to get from where the power module goes over to something else in the power ground circuit like the fuel rail ground.

    Brian
    What is the difference between the power module, and the smec "power module"? Could you not use only the logic module part of the smec with the old power module?

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