Martin86Cherokee

Hi!

I recently bought a 1986 2-door custom(base) XJ with the 2.5l AMC 150 w/manual transmission. It has roughly 140k miles on it and has had a few owners and some modifications done to it, the main mod being retrofitting a 97 dashboard, wiring harness/ecu etc. The main issue is that it cranks and starts but then shuts down, I've checked the ASD relay, the cam position sensor and they don't seem to be the problem, but after removing the center console I found a duct-taped and zip tied homemade box with a circuit board and small Transmitter inside( it says 56009389 on it). From what I can gather, this is part of the anti theft system (immobilizer) and since I only have the black triangle shaped key with no fob/remote on it I can't start the car. The previous two owners have not been able to get it started so it has been passed along. I suspect that someone down the line lost the key or that it stopped working and that getting a new one programmed would cost too much so they dumped the car onto the next guy as a project.

So this brings me to the issue of what to do next. The plan is to get it as close to stock as possible and put an 84-96 dashboard in it which means I don't necessarily want to spend too much time on trying to get the 97 ECU working by bypassing the immobilizer, but it would be nice to see how the car runs. There doesn't seem to be a quick fix to this and the most realistic solution seems to be to remove the system and replace the ECU with a unit that does not have the immobilizer programmed into it. I've tried disconnecting the battery to reset the ecu and disconnect all the plugs to the immobilizer system without any luck, seems like the ECU knows that there should be an immobilizer there and won't start if it isn't disabled by the transmitter. Does anyone know a "quick fix" to this other than flashing/replacing the ECU?

Also, as far as ECUs go, will an 87-90 ECU work with the 86? 86 seems like an odd year and the ECUs are hard to find, but I have read that 87-90 should work. I have the correct wiring harness for it, just not the ECU.

Thanks in advance and I hope I made sense. This is my first project car and I'm not planning on using it as a daily driver or relying on it so I'm not in a hurry

awg

I am surprised a 97 OBD2 PCM works at all with an early engine, presumably it must have the same sensors

From what I know of 97 immobilsers there is no easy way out, its an XJ death sentence (minimum is matching 97 ECU and ignition barrel)

That means reverting back to the original dash, wiring harness, and presumably ancient electronics..which is actually not a good solution

It may be cheaper (and less time consuming) to buy another one, either as a source of spares, or a goer (I have an exact going spare for my '96, I took its fuel pump the other day )

Martin86Cherokee

Not sure how he was able to make it work so I'll have to do some more research. Presumably he drove it like that for several years and there is no mention/record of an engine swap although I'm not ruling that out. I've ordered the Haynes manual to see if I can identify what has been swapped with the help of some additional google searching. Like I mentioned I have the correct wiring harness and dash. It's "just" the new dash and engine bay that has had the newer harness put in. Lots if cables are tucked away and not hooked up to anything. You bring up a good point about the sensors which I'll have to look into.

I'll do some digging around before I dig myself into a hole, but the car was cheap and I'm not in too deep. It's pretty clean with very little rust other than some spots in the floor so it would be a shame to let it go. I'm keeping my eyes out for a donor car, but they aren't all that common here in Norway, especially with the 2.5l.

Appreciate any input

Saudade

Based on what I found online, the 86 2.5l was throttle body injected using the RENIX fuel management system. So a Renix ecu might work but it would have to be for the 4 cyl, not the 6.

You can find some documentation here:

https://xjjeeps.com/

Since yours is a "blend" of different years, you may need the '97 docs as well.

The immobilizer used a sensor that surrounded the ignition switch to detect the chip in the key. That sensor wouldn't fit in the stock '86 steering column. So unless the column was swapped as well, I can't see how that would have worked. Possibly, it's an aftermarket system. If so there some kind of module patched into the harness. I have mine under the center console.

Good Luck!!

Martin86Cherokee

Thank you! I’ll check out the link.

There is no sensor around the ignition, but I found a box stashed under the center console with a small transmitter taped to it. I’ll add some pictures when I get a chance, maybe someone will recognize the unit. From what I can find jeep had an option to add the anti theft device in 97-98 before the ignition mounted system was added in 99, but don’t take my word for it!

btw: The steering column was replaced too. I think I’ll go for a full harness swap and try to get my hands on an older model steering column.

Martin86Cherokee

You were right! Your comment made me dig a little more and it seems like there has been an engine swap at some point. The cast number on the block indicates it was cast in 95, maybe not assembled until 97(?) Throttle body, intake manifold and transfer case all come up as matching a 97. The air filter housing is strange, I can't find a similar one except from one picture on a Comanche forum that's supposedly from a 99 cherokee. It has an additional sealed box where it mounts to the throttle body and has brackets that bolt on to the valve cover. The sticker on the valve cover is worn out and I can't make out what it says, but I can't find any valve covers with mounts either.

Still trying to decide what to do, but the body is just too nice, minimal rust and I love the 2-door. Just not loving the 97 dash in a 86 so I want to return the interior to the 80s or early 90s and maybe do an engine swap if I can find another 2.5 in decent shape. Modifying the fire wall and putting a 4.0 in there is tempting as they are more powerful and easier to find, but I realise it's not just a simple swap so we'll see. I'm totally ok with this being a long term project and that sourcing parts may take a while, the search for a donor car is on The goal is to have a classic 80s weekend cruiser.

lawsoncl

FYI, going back to a Renix ECU will require changing sensors AND the flexplate.

awg

If you are saying there is a 2.5L '97 with immobiliser and manual trans, the "simplest" way out is to download the '97 FSM and Parts Manuals

This should confirm if that model came with a factory immobilser

If it did (which we will assume is likely), that means you either need from a matching spec wreck, the PCM and Ignition assembly with key

This might be hard to find, but should get your engine running

Its possible a later combo will work. We dont have 2.5 Manuals here

To the best of my knowledge there is no way to "trick" a failed immobiliser

its possible some part of the wiring to that circuit is incomplete or damaged

Martin86Cherokee

Alright, so I think I may have figured out why it won't start. I found what I have identified as a keyless entry receiver with a transmitter taped to it, if this unit fails the car won't start. A possible solution is to get a new receiver, but the only one I can find is a used unit for 250EUR on ebay and I'm not sure I'm willing to bet that will work tbh. I found an old post on a norwegian off-road forum where the solution was to get a replacement unit so in theory it should work.

The car does not have any power going to the doors so no power windows, locks etc. On the 1997 XJ, the unit is placed in the dome light, but since my car is an 86 they must have placed it under the center console to hide it. The harness that the receiver is attached to has a few connectors by the interior fuse box on the passenger side and there are two sets of black and red wires that come out of the harness. One set is spliced into the OBDII connector and from there it goes up behind the dash and is spliced into one of the gauge cluster connectors. The other set of red/black wires goes into the engine bay and is spliced into one of the connectors that attach to the ECU. I can't find or see any shorted wires but it's hard to inspect it properly and the black/red wires have been zip-tied to various parts of the wiring harness so there may be some damage that I can't see.

In case anyone else wonders the part number for the little black transmitter is: 56009389 and the receiver is part number: 56009387AB


This comes up as a keyless entry reciever on moparpartsgiant.com

awg

replace the keyless entry system with a cheap aftermarket should solve the door lock issue

but you need to get the engine start issue solved first

sounds like you have good working knowledge

download the manuals I said. trust me, you need to. I have them if you cannot, but they are very large

in my opinion, its possible a '96 Manual PCM might solve the issue, as it is OBD2, and NO IMMOBILISER

It also has a TCM that is not fully interdependent to the PCM, but you would still want a '96 MANUAL PCM (or a CEL may be thrown)

Its a gamble, but I obtained a spare 96 PCM for $100, so it would be a cheap easy shot if that worked

Martin86Cherokee

I should clarify the door lock. The 86 seems to have come as basic as basic gets, no power door windows/locks etc, doesn't even have rear wiper! None of that has been added when the 97 harness was put in and I'm fine with that. I kind of think it's cool, especially since I don't plan on this being a daily driver. I suspect the car originally came without the rear seats and was registered as a cargo van. So the only issue is the no-start, I'll get to reading the manuals and looking for a 96 PCM

A Norwegian not so fun-fun fact: There is a pretty hefty one-time tax on passenger vehicles in Norway so registering a vehicle as cargo van is a workaround if you want a 4x4 or large SUV, the downside is that you have to have a cargo barrier net behind the front row and no rear seats. After 20 years you can install the rear seats and register the car as a passenger vehicle without paying the tax. All of the cars come with the rear seats/carpets etc which you have to store for 20 years if you want to install them once the car is 20 years old... Pure nonsense and cars are literally half the price in Sweden. A quick search on a used car site a 2024 Land Cruiser (prado) with sub 5k miles is $70k as a cargo van and a 2021 with 20k miles is $120k as a passenger vehicle. Land Rovers are commonly referred to as stock market tractors as only white collar wealthy people can afford them.

Thanks again, really appreciate your input!

awg

I can see an easy workaround.

My XJ has the rear upright removed, as I rarely need to transport more than 2

Ona previous SUV, I built a custom cargo barrier (I still have it, brilliant job, use galvanised metal !)

Reg it with rear seat back out and cargo barrier in..

then just remove cargo barrier for daily use

I can fill my XJ up, and even sleep in the back, and I am 6ft

Martin86Cherokee

Good idea! but it's risky because you get green license plates to indicate that it is not a passenger vehicle. If you get stopped they will not just fine you, but send a bill for the tax difference which in the previous LC example would be rougly $50K!

Saudade

And I though passing smog test here was stressful enough!!

dmoe69

This is a crazy story and I hope you figure it out. There was no 4 cylinder available for 1997, so either that isn't a 1997 ECU or it never ran. If it starts and runs for a few seconds, have you tried putting a jumper across the fuel pump ballast resistor?