The "WTH is this plug under my hood?!" game

I have a 2000 XJ and I've been putting in a 1998 engine harness, distributor and coil. Therefore, many of the sensors are for a 2000, and the harness for the '98 seems to be different in a few ways. What's left over is a few sensors that I likely need the older version of, a few plugs I don't know where they go to and could use some help, etc.

So, while this could be totally a waste of time, I thought I would post pics of my problem areas and see if you can figure it out what any of these go to!

Passenger Side Firewall


Passenger side, on motor, near firewall


some kind of sensor by the oil filter and distributor


wire and plug coming from the distributor


Passenger side, between battery and block



Thanks =)

spinaldex said:

Passenger side, on motor, near firewall

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I'm sure I'm probably wrong, but I believe this detects pre-ignition or pinging. Part of the smog system.

Original_MudButt said:

I'm sure I'm probably wrong, but I believe this detects pre-ignition or pinging. Part of the smog system.

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Its an ignition capacitor, for suppressing ignition noise over your radio. I broke mine when I did the head gasket, just taped up the plug and let it dangle, haven't had any issues and everything works as it should.

spinaldex said:

some kind of sensor by the oil filter and distributor

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That is the oil pressure sending unit that tells the gauge on the dash what the oil pressure is.

spinaldex said:

wire and plug coming from the distributor

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The Distributor still has a Camshaft position sensor inside of the distributor and this is the plug for the sensor.

What I can't figure out is where I plug the camshaft position sensor in to on the harness. I can't locate a matching plug anywhere ...

spinaldex said:

I have a 2000 XJ and I've been putting in a 1998 engine harness, distributor and coil. Therefore, many of the sensors are for a 2000, and the harness for the '98 seems to be different in a few ways. What's left over is a few sensors that I likely need the older version of, a few plugs I don't know where they go to and could use some help, etc.

So, while this could be totally a waste of time, I thought I would post pics of my problem areas and see if you can figure it out what any of these go to!

Passenger Side Firewall

That's the underhood light

Passenger side, on motor, near firewall

That's an EMI filter for the ignition/charging system to prevent electrical noise in the radio and other systems.

some kind of sensor by the oil filter and distributor

That's the oil pressure sensor and you're holding what looks like the original cam sensor connector from an 00, if you look about 3 inches up the harness you should see the connector for the oil pressure sensor.

wire and plug coming from the distributor

If you have the 00 engine harness still in the jeep you're not going to have a plug for that.

Passenger side, between battery and block

Looks like the plug for the back of the alternator or the high pressure switch on the AC line in the background of the picture.


Thanks =)

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Do you still have the 2000 engine harness installed or did you install the 98 engine harness? :gee:

spinaldex said:

I have a 2000 XJ and I've been putting in a 1998 engine harness, distributor and coil. Therefore, many of the sensors are for a 2000, and the harness for the '98 seems to be different in a few ways. What's left over is a few sensors that I likely need the older version of, a few plugs I don't know where they go to and could use some help, etc.

So, while this could be totally a waste of time, I thought I would post pics of my problem areas and see if you can figure it out what any of these go to!

Passenger Side Firewall

Underhood lamp



wire and plug coming from the distributor


Passenger side, between battery and block

Battery temp

Thanks =)

Click to expand...

.

I put in the 1998 engine harness already. The plugs that are left are the ones I couldn't figure out what to put in there. Based on what you guys have described already, it looks like:

- I need a '98 Oil Pressure Sending Unit (plug is different)
- I need a '98 Oil Pressure Sending Unit (plug is different)
- I can ignore the underhood lamp


I still can't figure out where the plug from the distributor goes to. I can't find a single plug on the harness that is small with just 2 plugs on it like that.

spinaldex said:

I still can't figure out where the plug from the distributor goes to. I can't find a single plug on the harness that is small with just 2 plugs on it like that.

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It should be on the harness that runs behind the distributor and connects to the ignition coil and continues on to connect to the group of grounds down by the alternator on the block.

Also the oil pressure sensor on the 98 is two pins and is a rather large connector.



Are you 100% sure you don't have the 00 harness still there, because that connector you showed next to the oil pressure sensor looks a lot like the Cam sensor plug on the 00 harness.

theres a sub-harness that comes from the battery area to the alt, a/c, coil and distrib that I bet you are missing from the '98

Ok, so the engine harness is *technically* two harnesses in one. The outside one that includes the fusebox, and the inside one that connects to the injectors, throttle body sensors, and to the distributor, etc.

I pulled out both in my 2000.

I had a buddy who was parting out a 98 give me both harnesses, distributor, PCM and coil out of the other cherokee.

I put in both. One reason I know I have the right inside harness (the one with the fuel injectors and distributor connectors) in there, is that the fuel injectors on the 00 are different than on 98 because the plugs are different. To get injectors to work on the 98 harness I picked up some used injectors that came out of a '98 TJ. So, I *must* have the right harness in there =)

And, there's differences. My 00 had ABS and the 98 harness doesn't have the ABS plug. The 00 only had 4 sensors at the throttle body and the 98 has 5 plugs come out of the same spot and I have no clue what the 5th does since I don't have a place to plug it in.

But, there's other issues. Obviously there's a couple of sensors with different plugs. That makes sense and I can pickup different ones. But, the plugs don't fit for the distributor nor for some sensor that plugs in to the AC compressor (the one thats upside down facing the ground). That might be another case of "buy the old sensor" or something, but there's clearly something not right here.

I've gone over the harness 10x so far with a flashlight to make sure I'm not just missing a connector for the distributor.

Not sure what to think here. My buddy is out of town but I sent him a quick message to check 100% that all of these came out of the same rig. If there was a mixup and the plugs differed on the distributors over the years, maybe that's it??

I'm trying to figure this out. The model number on the 91-97 distributors is different than the 98-99. I wonder if the plug changed and my buddy grabbed the wrong one (he parts out a lot of rigs). I wonder if the coil is the same story.

Anyone have a 98-99 and could take a picture of the plug coming off of the distributor and the one that connects to the coil?

Ok, the plugs *are* different on the distributor, coil and the oil pressure sending unit in 98-99. So, that explains that. Guess I'll need to get my hands on those.

Now, what's left:

- Can anyone verify if 98 had an ignition capacitor (which is basically an EMI filter)?I can't find it using any parts store tools. Also, it has a single wire connector on it and any plugs I see near it on the harness all have at least 2. I'm wondering if it was not factory for certain years? Does anyone have a 98-99 and can verify what the plug and sensor look like on their block? Its half way down on the rear passenger side of the motor.



There's two other plugs/sensors I'm unsure of that haven't been listed here:

This is a picture of the 5th plug that comes out at the harness by the throttle body. Like I said earlier, the 2000-2001 only have 4 plugs there. So, I'm curious if anyone knows what this goes to?



The other is a sensor of some sort on the metal hoses that go to the back of the AC. When I looked up pictures of earlier model AC's it doesn't look like they had them, so I wonder if this was something added on the 00+ Jeeps? If so, any reason I should be concerned not having it hooked up?

spinaldex said:

Ok, the plugs *are* different on the distributor, coil and the oil pressure sending unit in 98-99. So, that explains that. Guess I'll need to get my hands on those.

Now, what's left:

- Can anyone verify if 98 had an ignition capacitor (which is basically an EMI filter)?I can't find it using any parts store tools. Also, it has a single wire connector on it and any plugs I see near it on the harness all have at least 2. I'm wondering if it was not factory for certain years? Does anyone have a 98-99 and can verify what the plug and sensor look like on their block? Its half way down on the rear passenger side of the motor.



There's two other plugs/sensors I'm unsure of that haven't been listed here:

This is a picture of the 5th plug that comes out at the harness by the throttle body. Like I said earlier, the 2000-2001 only have 4 plugs there. So, I'm curious if anyone knows what this goes to?

That goes down to your CPS

The other is a sensor of some sort on the metal hoses that go to the back of the AC. When I looked up pictures of earlier model AC's it doesn't look like they had them, so I wonder if this was something added on the 00+ Jeeps? If so, any reason I should be concerned not having it hooked up?

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You need to replace that switch with one form a 98 (it unscrews and has a shader valve behind it) and that plugs into your mysterious 2 pin connector you have by the battery.

Do you know what the switch for the AC is called? I want to make sure I pickup the right one, thanks!


Also, the 5th plug .. the wire connector was pretty short stock (only a couple inches). I originally thought it went to one of the plugs on the other side of the throttle body so I lengthened it then realized it wouldn't reach and the other black plug was the one that had to go there. How would a 2" long wire reach all the way down to the top of the transmission?

the CPS has a long pigtail to reach the harness connector

switch for the ac is the high pressure cut out - rock auto has it listed as ac clutch switch

Yep, confirmed, thanks Digger. The CPS plug fell back down so I didn't see it.

Thanks for the heads up on the AC clutch switch.

Now I just need to find some good deals on these parts =)

Ok, so I'm having a trouble with the pressure switch on the AC for this swap. The electrical side plugs differ (4 prong vs 2 prong), and the threads on the schrader ends differ as well. So, its not as simple as just using the '98 or the '00. Here's a few pictures to show the problem.

Thread comparison:



1998 Plug


2000 Plug


Profile


Any suggestions on what I can do? Maybe there's some kind of adapter that exists to allow the 1998 switch to thread in to some schrader end, and then that threads in to the one on the AC??

Here's some reading on the 2000/01 AC system and a schematic that shows the pressure switch functions. Note that the dual function switch is different than the prior years high pressure switch.

So, if the function of this switch and the unit has changed, that would mean it would not be possible to wire this in to the '98 PCM and wiring harness, correct?