Hi Guys, I am looking for a little bit more information on a wiring harness swap. I was recently gifted a 2002 Sc2 that's been sitting for some time and a mouse has caused havoc on the engine wiring harness.
Question is what's the best way to remove the engine harness and what year models would be compatible for replacement? I would repair it but the harness has at least 10 spots I have found that's chewed. Its a 3 door Sc2 coupe with auto windows and a manual transmission. Its also a dohc. Any help or information would be greatly apricated and if someone happens to have a exact parts car I would also possibly be interested in purchasing a harness. Thank you.

 

​​​​Does the car currently run? How many miles on it? Does the body and engine condition make this a worthwhile effort?

Before doing anything else, I would do a compression check, wet and dry and post the values here so that we may assess general engine health. You can rotate the crank by hand if need be.

Once you know what you're working with, you can make an informed decision as to whether complete replacement or repair is in order.

You may have to repair some of it just to see if the car runs.

 

I have heard the car run in the past, it was a family friend who had it and it was parked for about a year due to a leaking radiator. They had no clue the wires were chewed till I talked about buying it from them and discovered the wires were chewed when I went to look at it so they just gave it to me since it needed more work then they thought. Body is in great shape and no cracked plastics and clutch has around 30,000 on it since it was replaced and the engine has around 150,000 miles.

 

New clutch at 120K? Pretty rough, although the third generation S cars had a differently designed supposedly self-adjusting clutch which people generally refer to as the POS clutch.

Saturn S car DOHCs are prone to oil burning as the oil control rings pass increasing amounts of oil and the valve guide seals leak oil into the cylinders. General ring wear is common.

Both SC2s I owned went south engine wise at 185k.
some last up to 250k before the substandard compression and massive oil consumption beckons for a rebuild.

This is why I'm strongly suggesting for you to do a compression test, wet and dry, as step 1.

I suppose step zero would be to check the oil. If the oil is low, there is a chance that the previous owners did not always attend to the level which is critical to the longevity of these engines.

I will assume you also do not know whether the vehicle overheated when the radiator developed the leak. But you can assess how much of the coolant is missing by draining it. My point is it may have compromised the head gasket or warped the head depending on how it got.

It's very easy to get something like this that has sentimental value and have that partially influence your decisions regarding the path forward.

My doom and gloom worst case explanations are not meant to rain on your parade. They are, however, some of the things you need to consider before determining what to do on the larger scale.

For example, if the engine is pretty worn out, if you decide that you want to keep the car, it may make more sense to find a replacement engine at the same time you put the new harness on, since you'll have to disconnect everything under the hood anyway to swap the engine. Ideally your decision on your path forward should be rooted in logic, but this is coming from a guy refreshing a 1995 SC2 one owner car that I have loved to drive since it was purchased.

Has been driven once every two weeks for the last decade except for the 3 years it sat under a tree.

Off topic as usual.

Just trying to help you guide you on the path that makes the most sense. And to do that, we really need to know the general health of the engine, which means compression check. You can do a loan a tool from AutoZone or similar. It's free.

 

Forgot to mention. If the mice have been around, do not turn on the blower motor for the HVAC before removing the blower motor with attached squirrel cage and cleaning out the rodent nest. You don't want to blow that shyat literally all through the vents.

Also check above the gas tank. Both areas are prime nesting spots as they are out of the wind in the winter.

After the compression test.

 

I just checked the compression today, I ran a jumper to the starter to crank the engine without having to mess with the wiring. Oil was dark but wasn't low.
Cylinder 1 -170
Cylinder 2- 175
Cylinder 3- 165
Cylinder 4- 170

I was also informed by the family member that it was never overheated and was parked when they noticed the radiator leaking and they didn't fix it due to having 2 almost new cars after owning it for the past 13 years and it was just a spare car for the last few years.

Now comes the question with replacing or repairing the harness, was there different harnesses for manual / auto trans and manual / auto windows? Would a harness from any S series car work? I could repair the current harness but I started pulling it and there's a lot of chew marks and a few chewed through wires and I think possibly it might be better to get a replacement harness if I could track one down just for reliability.

My reason for wanting to repair this car in the first place is its identical to my first car and with it being a manual trans I feel like once I get the harness repaired and radiator replaced, it should be pretty reliable. The current radiator started leaking at the top corner as I can see all the residue left.

 

Derf will have to answer harness questions. I know the the harnesses are different on the L series cars. I would imagine that the twin cam and single cam cars have different front harnesses and the stick shift and automatic cars would also be different. Janmar just got through with an engine swap involving a late S series, maybe he can help also. The electric windows should not affect the engine harness, at least it doesn’t on an L series car.

 

Reasonable for a dry test of a vehicle with that many miles on it. How much higher did the compression go when you added the oil to each cylinder on the wet test?

Off the top of my head

1. I expect the third generation DOHCs to have different harnesses than the second and first generation. This narrows your daughter range to possibly 99 or 2000 to 2002.
2. I suspect the SL2 and SC2 harnesses to be very similar for 2001 and 2002. I say this because I believe the third generation sedan SL2 appeared in 99 but the SC2 appeared in 2000. Probably took him a few years to standardize between the two, or maybe they never did.
3. The S cars, at least the earlier SC2s, did not seem to have any pigtails that were not attached to something, meaning the harnesses seemed to only have what was necessary to match the exact configuration of the car. This is not true in all cases, but it always seemed that anything I would have wanted to add to my SC2s that was not factory specified did not have the needed wiring already integrated into the harness. The way they sold the cars, however, was that the SC2 automatically came with the power package, so that took care of a ton of stuff that was all included in one harness or omitted from the harness. Yes you could get an SC1 with power stuff, so I suppose there's a separate harness for that.
4. You need to define what you intend to swap out, literally, when you refer to the harness. Do you mean the entire wiring harness for the entire vehicle, only under the hood plus whatever doesn't work?

Oh, be sure to check your fuel lines they are rather tasty to critters. I don't know if they were still using nylon in 2002 as they were in 95. You'll have to check if it's a problem.

Back to the harness.

I think it is best to decide exactly what chunk of wiring you intend to replace. If it's the entire vehicle, that's fine but a lot of work. But if you can determine the exact damage to specific circuits, you may be able to splice in just the part of the harness that resides in the engine bay. And fix the odd problem on a per wire basis.

Remember that since this vehicle has a BCM, it will have the BCM controlling most of the internal functions of the vehicle, and unless those wires are chewed up, I can't see your reason you would want to deal with all of that interior wiring just for the sake of replacing it. If it's damaged, of course....

1. I expect the manual versus Auto trans to have different harnesses since the manual has no valve body or TCM.
2. I would go to a site like gmpartsgiant. com and enter your VIN, then go harness shopping. What you are really looking for is the part number for the harness in your car and fitment information as to what other vehicles if any share use of the same harness.

Congratulations. I think I can finally fall back to sleep now

 

Thank you for all the insight. My thought was to replace just the wiring under the hood, I have put a battery to it and was able to get power inside the car and to the cluster so I think the wiring inside will be okay, there was a mouse nest in the injector area and they chewed the wiring by the injectors and ate random parts of the harness on the right side of the motor. My thought was to just disconnect everything from the fuse box under the hood and replace the wiring in the engine bay to start and hope they didn't get to any wiring inside. I will keep you updated on if I can figure out or track down a replacement harness.