Cruise Control Wiring Diagram Help

HuskerJeep

HuskerJeep

TJ Enthusiast
Joined
Jan 17, 2019
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Location
Omaha, NE
I'm installing factory cruise in my '98. I do not have the magic plug under the hood, and I did not have the correct clockspring either so I am basically having to do this from scratch. Tonight, I started tracing all the wires I would need for the overlay harness, and I'm hoping for some help on something.

It seems like most of the wiring is already there under the dash. Take a look at my marked up diagrams below - the highlighted lines are the wires I assumed I would need to install as part of the harness, but as you can see, most are already there.

My confusion is on the wire connecting the Vehicle Speed Control Servo to C107 on it's way to the Stop Lamp Switch (wire V30 20 DB/RD). It's definitely there on both sides of C107 in the E11 slot. So...where the hell is the other end that's supposed to hook to the Servo (which wasn't there, and there is no pigtail under the hood). What am I missing?

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Find the mopar cruise control install document. I have it at home, but not at work.

Make sure you have the correct buttons for your year, there were 3 different sets depending on model year.
 
whitrzac said:
Find the mopar cruise control install document. I have it at home, but not at work.

Make sure you have the correct buttons for your year, there were 3 different sets depending on model year.
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Yeah, I have a copy of that; it's not helpful in my case though since I'm trying to create my own overlay harness and it seems like that document is from the later TJ years since the wiring diagram doesn't match my '98.

I'm pretty certain I have the right switches, but I'm not even to that point yet.
 
Interesting. I took a look through your wiring diagram but it doesn't show a figure of the harness and connector location for the vehicle speed control servo which if I'm understanding you correctly is the connector you need to find right? This little guy? The harness diagram in your manual doesn't show a diagram but only lists it as being "at the speed control servo" which doesn't help much.

104768


You say that you've verified the existence of all the highlighted wires, you verified that you have wires in positions C4, C5, & C11 on connector C1 of the PCM.

Do you have a C180 connector? That could be another place to check but you bypassed on your diagram, so I assume that your config is not "LHD drive ABS except DRL?
 
qslim said:
Interesting. I took a look through your wiring diagram but it doesn't show a figure of the harness and connector location for the vehicle speed control servo which if I'm understanding you correctly is the connector you need to find right? This little guy? The harness diagram in your manual doesn't show a diagram but only lists it as being "at the speed control servo" which doesn't help much.

View attachment 104768

You say that you've verified the existence of all the highlighted wires, you verified that you have wires in positions C4, C5, & C11 on connector C1 of the PCM.

Do you have a C180 connector? That could be another place to check but you bypassed on your diagram, so I assume that your config is not "LHD drive ABS except DRL?
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Good questions, thanks for digging into it for me.

The Vehicle Speed Control Servo connector you have shown there is the "pigtail" that is commonly pre-wired on lots of other TJ's and connects directly to the servo. This is typically zip-tied or taped to the firewall/fender near the master cylinder if it's pre-wired. I don't have that from the factory, so when I got my servo from the junkyard, I clipped it off and have to wire it up now. Here's what mine looks like right now, you can see the 4 wires hanging there:

IMG_2532.jpg


I have verified the existence of the highlighted wires, but I have not opened up the PCM yet to confirm that they land on the pins there. That's wrapped up pretty tight, so I'd have to cut the tape and pull back the covering to do that.

I checked on connector C180 - I'm pretty sure this is only included if the TJ has DRL or ABS; I have neither, and I couldn't find a plug that looked like that anyway. After searching the layout diagrams, this would be up by the master cylinder as well, but there isn't anything there.

All that leads me to believe that the DB/RD wire makes it's way into the engine bay, and could possibly terminate somewhere in the main harness, inside the loom, on it's way to the PCM.
 
It's faster to just run new wires than it is to find the old ones.

Land the wires from the servo on the correct ECU pins, 2 on the brake switch and 2 on the clock spring.

You will need ecu pins, I just cut a plug off from a junked XJ and used those. Be careful with the plugs they're fragile
 
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whitrzac said:
It's faster to just run new wires than it is to find the old ones.

Land the wires from the servo on the correct ECU pins, 2 on the brake switch and 2 on the clock spring.

You will need ecu pins, I just cut a plug off from a junked XJ and used those. Be careful with the plugs they're fragile
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I may end up doing that, but want to make sure I'm not missing something simpler.

If I understand correctly, you're suggesting I clip the wire coming out of C107 (DB/RD that runs into the firewall) and run a new wire from the end of that wire to my new wire on the end of my Servo (DB/RD)? No concern about the old wire in the harness?

I don't think I need to do anything with the Brake Switch or Clockspring since all that wiring is already there. Then the 2 to the PCM from the Servo (I also clipped the PCM plug from an XJ at the junkyard, so I have pins).

I'm just not sure why all the wires are where they are supposed to be in the plugs/pins, but there is no pigtail under the hood. Makes me think they are all terminated somewhere in the harness.
 
HuskerJeep said:
If I understand correctly, you're suggesting I clip the wire coming out of C107 (DB/RD that runs into the firewall) and run a new wire from the end of that wire to my new wire on the end of my Servo (DB/RD)? No concern about the old wire in the harness?
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Nah, you can leave that sucker in there, it's not doing anything.

HuskerJeep said:
I have verified the existence of the highlighted wires, but I have not opened up the PCM yet to confirm that they land on the pins there. That's wrapped up pretty tight, so I'd have to cut the tape and pull back the covering to do that.
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Maybe I'm misunderstanding... All you should have to do is just unplug C1 of the PCM and verify the pins are there in those positions. You're going to have to unwrap all of that anyway to find the wires and splice in to piggyback to the solenoid right? I'm not a TJ expert by any means but wiring is something I do for living... If I'm off track let me know.

HuskerJeep said:
I'm just not sure why all the wires are where they are supposed to be in the plugs/pins, but there is no pigtail under the hood. Makes me think they are all terminated somewhere in the harness.
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On a 20 year old truck who knows. Maybe they made different harnesses to different specs, instead of terminating these wires on the speed control servo connector they just wrap them up in the harness. Like @whitrzac said, piggybacking wires at this point is going to be your best bet.
 
Thanks for the replies on this.

I had a little time to work on it last night and got my new clockspring installed. Since all the wiring was there under the dash, even though I don't have the pigtail in the engine bay, my theory was that I would be able to install the clockspring & steering wheel switches and push the "On" button on wheel and the light would illuminate in the gauge panel even though I couldn't actually use it since the servo isn't hooked up yet.

It worked. Meaning all I have to wire is the 4 wires from the servo.

So, it seems that there are TJ's out there with no cruise wiring at all, some with the clockspring and engine bay pigtail, some with just the pigtail, some with just the clockspring, and mine that didn't have the clockspring or pigtail but is wired in the harness.

IMG_2548.jpg


IMG_2533.jpg
 
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I did not have the clock spring either but I did have the pig tail under the hood. Don't over think think it too much the majority of the wiring is correct and I am not sure where they will have terminated the DB/RD wire off your stop lamp switch. At the end of the day you can wire directly from the pig tail into the locations it needs to complete your system. The black wire of your pig tail is ground, the dark blue/red wire is the stop switch wire you have highlighted with ? regarding its destination, the light green/red wire goes to C5 on the PCM plug one and the tan/red wire goes to C4 on the PCM plug one. where you tap in is up to you, if you are really OCD pull them back to where they currently terminate and make your connections there, if your not too worried about the looks just run your new wires over and cut them back a few inches from the PCM/stop lamp switch and make your connects there.

Sorry about the slow response I was away for a while due to a major surgery just really getting back to normal.

Kevin.
 
For anyone who stumbles on this later, I got this figured out and my cruise is working great.

Turns out that I did have the C180 plug even though I don’t have ABS or DRL. That plug is also used for the Evap system, and my 4 cruise servo wires were terminated on the harness side of that plug.

I went ahead and clipped those off and tied my pigtail in and everything worked. No need to do anything with the PCM.

Here’s a pic of that plug for anyone else in the same situation later. My finger is on C180 and you can see my pigtail down to my servo next to it.

9F6DF5F4-DAB6-45C3-AF4F-DEBD52B87EA5.jpeg
 
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Nice! Glad you figured it out and thanks for posting the resolution for everyone else
 
Shandara said:
I did not have the clock spring either but I did have the pig tail under the hood. Don't over think think it too much the majority of the wiring is correct and I am not sure where they will have terminated the DB/RD wire off your stop lamp switch. At the end of the day you can wire directly from the pig tail into the locations it needs to complete your system. The black wire of your pig tail is ground, the dark blue/red wire is the stop switch wire you have highlighted with ? regarding its destination, the light green/red wire goes to C5 on the PCM plug one and the tan/red wire goes to C4 on the PCM plug one. where you tap in is up to you, if you are really OCD pull them back to where they currently terminate and make your connections there, if your not too worried about the looks just run your new wires over and cut them back a few inches from the PCM/stop lamp switch and make your connects there.

Sorry about the slow response I was away for a while due to a major surgery just really getting back to normal.

Kevin.
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We have talked briefly before. I have a 1998 Jeep tj, actually I have two of them. One for parts. The one that is for parts has cruise in it. My regular one don't. I'm thinking of putting the cruise in my regular one. The cruise in the old one don't work . I think due to a clock spring, but am not sure. Am I being foolish to consider this?
 
Ok so I have the clock spring and have them plugged into the switches. I have the servo, bracket, and lines I need. The only thing I do not have is the pigtail under the brake booster. What is this about the magical c180 plug, where can I find it, and how can I tap into it to make the cruise control work? I just really want to finishing this project. Help anybody?

HuskerJeep said:
For anyone who stumbles on this later, I got this figured out and my cruise is working great.

Turns out that I did have the C180 plug even though I don’t have ABS or DRL. That plug is also used for the Evap system, and my 4 cruise servo wires were terminated on the harness side of that plug.

I went ahead and clipped those off and tied my pigtail in and everything worked. No need to do anything with the PCM.

Here’s a pic of that plug for anyone else in the same situation later. My finger is on C180 and you can see my pigtail down to my servo next to it.

View attachment 106801
Click to expand...
 
Bobcat434 said:
Ok so I have the clock spring and have them plugged into the switches. I have the servo, bracket, and lines I need. The only thing I do not have is the pigtail under the brake cylinder. What is this about the magical c180 plug, where can I find it, and how can I tap into it to make the cruise control work? I just really want to finishing this project. Help anybody?
Click to expand...
The picture that I included on that post is the C180 plug with my finger on it. It's located just in front of the brake booster and is part of the evap system. I can't say for sure your Jeep has it, but that's where the wires terminated on mine.

Take a pic of your engine bay from the drivers side and I can tell you whether or not it's there.
 
Here, I found another picture a little further out that shows the C180 plug in relation to the master cylinder. C180 is circled in blue.
IMG_1674_LI.jpg
 
Looks like a different setup than mine (it’s a ‘99), I don’t see the plug from those photos.

If it’s not there, you’ll have to try tracing the wires back from certain points under the dash using the wiring diagram for your specific year as a guide. They changed wire coloring from year to year.

Good points to start would be the wires coming out of the steering column (from the clock spring), and the in/out of the stop lamp switch since it has to run through there.

I got to the point where I found all my wires under the dash and could see them going through the loom that went through the firewall into the engine bay. I thought they were just terminated in the harness in the engine bay until I found C180 (which not all Jeeps will use).
 
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