C115 - ECU to Instrument Panel (and one other)

[Gojira94]

 

Edit: I located the 87 electrical manual (thanks FiatSlug87), so the the 2nd connector numbers below are different between 87-88)

https://drive.google.com/file/d/1XBkojfjOdkg7X9ittvYaL0bRUj6qKc0G/view

 

I'll be doing a separate build thread on this basket case 87 MJ, but I have a couple questions as to where 2 connectors go. I've been going through all the wiring from firewall back and pulling out all sorts of other peoples' "great ideas" to get back to stock wiring. I'll make my own choices on what to add without hacking up the factory harnesses, with a more modular approach.

 

Connector #1: C115 - "ECU to Instrument Panel" on p.77 (2.5) and p.80 (4.0) of the '87 electrical manual, as part of the "Engine Control Harness" diagram and "EEC to I/P" in the inline connector views on p.60. Where does this connect/ what does it connect to? I've been through the 88 electrical manual linked here (and now the 87 electrical manual as well). That answered everything else on I found going through the dash. C115 is pictured in a couple pages of exploded diagrams toward the end but no answer as to what it plugs to and where that is. I'd like the wire color/ pinout as well.

 

 

Connector #2: I think it's C251 Cruise control clutch C260 Cruise Control Dump Valve Switch. The brake switch at C250 C249 is there on the brake pedal lever, connected. If there was a clutch switch on the stamped steel bracket 1/2" aft of the clutch pedal lever, it's gone now. If it had one, it would function (edit): possibly as 1) a clutch start switch and 2) cruise interrupt. Did these things from 1987 even have a clutch start/ neutral safety switch? (edit): Looking at the starter diagrams on p.14 it doesn't look appear so. This MJ doesn't have cruise, so I think I can tuck it away until I get sick of not having cruise and collect everything to add it lol.

 

 

Thanks!

 

Edited May 16, 2022 by Gojira94
Corrections/ clarification

[eaglescout526]

The second pic is for the 4wd as well if I remember right. I have seen 4wd Jeeps use the same switch/vac valve on 4wd set ups. It is not used for the cruise control at all. Course I have never plugged mine in so I have no idea if it will even affect anything being that mine is 2wd.

 

Not sure on the first one though. There are quite a few unconnected plugs that really don't go anywhere. AMC probably had things planned for a good chunk of the empty plugs and while some were used, it is unknown what they had planned for the others that go unused. Could always use a voltmeter and see if it has power.

[Ωhm]

88Electrical Manual

Connector#1: C115. Pg19_2.5L/Pg20_4.0L.

Connector#2: C260. Same pages as above.

I think I see a clutch pedal.

[Gojira94]

Ok, so found a couple things where I wasn't looking, auto trans related (I'm manual). C115 is as follows, for both 2.5 and 4.0 setups with 4-speed auto trans:

BLK/YEL pin H looks to be from TCU fuse to auto trans gear selector switch and power/comfort switch

TAN pin J appears to be power input signal between TCU and power/comfort switch

LT BLU w/TR pin K appears to be power/comfort switch ground from G102

 

C260 is:

LT BLU W/TR pin A is cruise/ trans switch to TCU for interrupt cruise  and torque converter unlock logic

BLK pin B shares ground with C115 at G102.

 

So both of these are auto trans related and won't ever be relevant to me. lol...

[Ωhm]

1 hour ago, Gojira94 said:

So both of these are auto trans related and won't ever be relevant to me. lol...

 

Now what I don’t know is C260 serves as a dual function switch. One is electrically for the purpose of disengaging the auto trans torque converter and the other is a mechanical vacuum dump for the cruise control (if equipped). So the question is, does the clutch pedal need the cruise/trans switch if you’re a Manual Trans with Cruise Control? Myself, IDK. Anyone with this setup (MT wCC)?

[eaglescout526]

38 minutes ago, Ωhm said:

So the question is, does the clutch pedal need the cruise/trans switch if you’re a Manual Trans with Cruise Control? Myself, IDK. Anyone with this setup (MT wCC)?

No it does not. When I made my cruise kits and installed mine, I used the GM dual vac switch for all set ups. It works the same way. Basically what most of the harnesses I have have is they have a clutch bypass plug(basically two metal prongs that plug into where the clutch switch goes) and it just relies on the dump valve at the brakes to stop cruise control(two stop shop for the system as it dumps vac and halts cruise operation). The clutch switch momentarily disengages cruise until the clutch is let go(hence the bypass prong). Plus the clutch switch is impossible to find at all for anything so it’s better to just have the auto trans set up. 

[Ωhm]

Thanks