Fried the engine computer. Can I get a used one?

Ok long story short I was messing with the aux fan wire that goes back to the computer and caused a short and looks as though I fried the computer. Can't get it to talk to a scanner just gives me a read error. So I am going to the junkyard tomorrow to find another one.

My Jeep is a 1997 4 door auto 4x4 Country model with just about everything you could get optioned on it. I know they went to OBD-II in 96 and they are very similar up to 2000 when they went to coil pack ignition system.

Can I grab the computer from any 96-99 Jeep or does it HAVE to be another 97? Also is replacing it with a used computer going to throw off my odometer? How about options on the Jeep, does the computer run any of those or is it JUST controlling the engine?

Just checked the inventory at my local pull-a-part and the only Jeeps after 95 that they have are a 98, 99, and 2000. Will any of those computer work in my 97? Need to get my Jeep back on the road!

as long as you get one from an auto it should be a plug and play, the only way it should mess with odometer reading is if yours is digital display

A 98 or 99 with the same motor should probably work (you might lose something dumb like the fuel gauge working right or the oil pressure gauge being different), a manual one will work fine but you will lose some TCU diagnostic capability, which actually is somewhat of a benefit if you want to put in a manual shifter for the AW4 later.

You can get the ECU reprogrammed somewhere to actually be the same as a 97 from what I understand - IIRC, sidewaysstarion on here knows someone who can do it.

EDIT: make sure the donor vehicle does not have SKIM!!!

nick86 said:

as long as you get one from an auto it should be a plug and play, the only way it should mess with odometer reading is if yours is digital display

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Mine is digital. All 97+ have the digital odometer. My main concern is when I did some searching (which didn't give me much that was relevant to my questions) they mentioned something about the 98+ having that vehicle security system with the chip in the key and I couldn't tell if they were talking about whether or not the programming was in the engine's computer itself and if it had to be programmed by the factory to work. My 97 was never available with such a system so if the 98 or 99 computers did have that kind of programming in them, will those computers work in my Jeep if the security equipment is absent?

kastein said:

EDIT: make sure the donor vehicle does not have SKIM!!!

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If I am correct that is the security system equipment I was referring to. How can I tell if it has the SKIM equipment? easiest way would be to look at the key fob for the panic button and the key if it is one of those keys I like to loving call the "fat head" keys with the chip in it. But these are junkyard cars that I will be pulling them from and I have never seen the keys in any of these cars and I have been in plenty of them. So what else can I look for to figure out if it was equipped with SKIM?

A 1997 XJ REQUIRES the use of a 1997 engine computer. Other years probably will not function.

Look for the gray SKIM keys or the SKIM chip reader module at the ignition cylinder.

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Tim_MN said:

A 1997 XJ REQUIRES the use of a 1997 engine computer. Other years probably will not function.

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just curious, where did you get this info?

The only electronics differences 97-98 that I'm aware of are:
* oil pressure sender changed from resistive to solid state type thus gauge may not work
* fuel level sender resistance curve may be different, have not checked this
* transmission input speed sensor added in 98 (this does not affect the ECU, just the TCU, AFAIK, and even if it does, it will still run, just will set a code)
* transmission output speed sensor type changed in 98 (see above)
* remote door unlock/lock remote receiver location changed from front of headliner between sunvisors to inside dome light or OHC (no electrical change, just a location change)
* SKIM added to some vehicles in 98 - you can tell based off the pics Tim posted. Don't use these as donors, they are more complicated to get working. IIRC SKIM can be disabled on an ECU if it hasn't been tripped yet and you have the matching key to go with it, but it's really more of a hassle than you want to deal with.

Unless I am mistaken all of those are unimportant. Worst case, some codes, it'll still run. Except the SKIM part, that's one you can't get around without the extra work.

And according to my sources/recollections, at least 97-99 computers are all electrically the same and can be reprogrammed to fit any requirement, 96s may be reprogrammable to work as well, and 00-01 will work on earlier years if reprogrammed but not vice versa due to different numbers of ignition coil drivers installed. I'm not 100% on any of the last paragraph, but I'd probably put money on it.

he can always get it reprogrammed to match the options he has or doesn't have, but I think right now he just want's it run. Unless I missed something in his post.

Add code retrieval to the list of "different but not necessary functions."

nick86 said:

he can always get it reprogrammed to match the options he has or doesn't have, but I think right now he just want's it run. Unless I missed something in his post.

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For the most part yes I want it to run. But I do want it to run and function as it was intended to i.e. all gauges working, no codes, transmission shifts, etc. If the 98 or 99 computers will work with reprogramming, how can it be reprogrammed and can the computer be swapped in and I can drive it to where ever the reprogramming can be done? Would love not to have this thing towed. Odds are this would be very pricey but how about a dealership? I priced up replacement ECUs from autozone and they are $200-$250 no programming needed. If I can get a used 98-99 and have it programmed for $150 or less, total, then that would be worth it but if it is only $20 off I am just better off with a new unit.

I don't know about Ga. but our Jeep dealer's shop rate is $90 per hour, so if it's a 2 hour job you just spent $180 to have a j/y pcm programmed. might be better to go with autozone deal

nick86 said:

I don't know about Ga. but our Jeep dealer's shop rate is $90 per hour, so if it's a 2 hour job you just spent $180 to have a j/y pcm programmed. might be better to go with autozone deal

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Yeah can't imagine it would be much different down here so I am thinking that I am going to just have to get the parts store unit to get this thing back up and running. This is a real bummer for me because the local pull a part sells them for $25.

I'd pick up the 98 for 25 bucks and see if it works. 25 is low enough a $ value for me to gamble that it would.

If it does, roll with it, or buy an autozone/ebay one (many ebay guys will program one to fit your requirements if you give them the vin/mileage/part number off your original ECU) and use that, while keeping the 98 one in reserve as a spare. As you know right now, having a spare part is never a bad thing when it's that small and cheap...

The 98 computer will work perfectly fine, the only thing that you might have an issue with would be the oil pressure gauge might not work as they changed the sensor between those years. If you still need an ECU I think I have a 97 XJ ecu laying around I could have programed and sent out to you.

So I picked up a used one from another member in my local chapter who said he got it from a wrecked parts Jeep he bought. He said it worked 2 years ago when his buddy tried it in his XJ in an attempt to sure a gremlin which it did not so he put back in the original computer.

I hooked up this computer and my Jeep still will not start. I tried hooking up my scanner and it still says link error and can't talk to the computer.

I made a careless mistake that I should have known better not to do. I was trying to find a power source to trigger a relay that would only come on when the Jeep is on. I was probing around with my voltmeter and came to the factory cooling fan relay. With the Jeep off as you can imagine only one terminal had power. With the Jeep on it had two with power though the one that now had power only gave me 11.93 volts. Though I would see if it was enough to trigger the relay and put a jumper wire in it. This was my horrible mistake as I was careless and let it touch something and grounded. I knew I had done something very wrong.

I checked the dash and sure enough there was the CEL. I grabbed my scanner and it said link error. That when I started to get a sickening feeling in my stomach. I tried to start the Jeep and it turns over but never fires. And the terminal I tried the jumper wire in that gave me 11.93 volts before now doesn't give me more than 2.38 volts with the Jeep on.

I plan to still pick up the new computer I ordered in hopes that this used one might be bad too.

But does anyone know where I can look next if the new computer doesn't fix my problem?

Curious, have you checked all the fuses under the dash and in the pdc?

kastein said:

Curious, have you checked all the fuses under the dash and in the pdc?

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I checked all the ones under the hood but I did not check the ones inside the cab. I got out the owners manual to see if there was any I thought would be relevant to anything I was messing with under the hood and did not see I thought would have anything to do with what I was messing with. I guess I can go out there and check them still and see if anything is blown in there. Anything I should start checking first in there?

I am at a total loss at this point and absolutely sick to my stomach over this.

Checked the fuse panel inside the cab and almost everything gave me a voltage reading and the ones that didn't the fuses were fine. I pulled out the silver fuse like things above which I believe are called circuit breakers and they all gave me a slight resistance of .002 which means they are tripped or blown. I check the relays under there and they all have power going to them although I don't know what any of them do. I think one is for the power locks (which still work) because when they actuate I can hear a clicking down in that area. One when I pulled it out I noticed my radar detector turned off which is plugged into the cigarette lighter.

One observation I made was that none of my gauges seem to be working. With both computers in the battery gauge reads nothing though I still have over 12 volts in the battery. When I switch the Jeep to on all the lights on the dash light up as they normally do but none of the gauges move at all. The oil pressure gauge bumps up just the slightest bit but not even enough to get to the first notch.

I am going to get the new computer in the morning to have a fresh one and see if I just got a bad used one too. But if that doesn't fix it then I have no idea what is wrong and what to check.

This is just a hunch, but check your rear O2 sensor harness and make sure it didn't come loose and short out on your driveshaft. Also check the front one as well where they wire goes around the front of the engine.