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.
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