double_0_7

My project 2000 4.0L sport. Okay, so weird...I just got off the phone with a mechanic. I couldn't figure out a few things that were still wrong, like getting the p1495 code for the leak detection pump when my vehicle doesn't have one. And o2 sensor faults when I just replaced them. I sent it to the mechanic to figure out a few things. Turns out, my XJ has the ECM from a WJ grand cherokee, 2001 he said, but I'm waiting for his guys to get back from lunch so I can get the exact VIN reading in the ECM.

Knowing that now, what other questions should I be asking? How do I know the motor is an XJ motor, or is it possible that at some point the engine was swapped due to needing repairs?

Vitals:
2000 Cherokee Sport
4-dr
4.0L auto
173,xxx miles
Steady idle, no overheating, no driveability issues.
Blackstone labs said, high metals, likely due to driving too long on the oil change, but nothing out of the ordinary.

CELs:
P1495 constant
o2 codes intermittent, P0151 etc...
No other codes

For the record, with my plans on having it as a project, and with some modifications in store anyway, I'm still happy with the truck.

The work I'm doing on the vehicle is to get everything in order for me to start doing mods.

PatHenry

There's no such thing as an XJ motor. Jeep used the same I6 in both XJ's and Grand Cherokees, so it's not that big a deal if the actual engine was taken from a GC or a regular XJ.
The electronics on the other hand... well, that's where your potential problems may be.

Is it an inline 6 cylinder engine? Can you read the head stamp? (Google identifying Jeep I6 head)

You can get the correct ECM part number by calling a Jeep dealership with your VIN.

It's very likely your motor -AT LEAST- has had the 0331 head replaced - which is a good thing.

double_0_7

I'm positive it's the inline 6.

When I get home, I'll have to look up how to identify the head.

I've heard in threads on here that not all 4.0Ls are interchangeable, so that's where my question about being the right engine came from. From Cruiser54's sticky:
" XJ Cherokee and ZJ Grand Cherokee 4.0L engine blocks interchange.

2000+ TJ Wrangler and WJ Grand Cherokee 4.0L engine blocks interchange.

XJ/ZJ blocks, and the 2000+ TJ/WJ blocks do not interchange without significant modifications. (1991 to 1995 YJ and 1997-1999 4.0L TJ Wrangler blocks will interchange in XJ/ZJ and visa-versa).

TJ/WJ 4.0L Engine blocks underwent clean sheet design changes effective in the 1999 WJ Grand and 2000 TJ Wrangler. These blocks are not interchangeable with XJ/ZJ engine blocks. The reason is motor mount bolt holes and belt driven accessory mounting bolt holes are in different locations, or not present at all, TJ/WJ vs. XJ/ZJ.


XJ: "Regular" (not Grand) Cherokees 84-01
ZJ: Grand Cherokee 93-98 (Gen1)
WJ: Grand Cherokee 99-04 (Gen2)
YJ: Wrangler 87-95 (Gen1)
TJ: Wrangler 97-06 (Gen2) "

PatHenry

Putting in a non-XJ compatible I6 (99+ GC, 00+ TJ) would drastically alter the engine accessory mount locations. So it's highly unlikely (though probably not impossible) you have that engine. I had a 00 TJ and the alternator was on the top and it had a spring-loaded tensioner. If your alternator is on the pass side bottom and you have the PS type mechanical tensioner, then you have the old style block.
There should be casting numbers to inspect for the block - I'm not sure off the top of my head where/what to check, but I'd start by assuming the block is original and look for that - if not, see if it's from the same year/model as the ECM or search on whatever numbers you find.

Changing the ECM is pretty easy to do (much, much easier than changing the engine) so I suspect they just changed the ECM and ignored the fact it threw engine codes.

Edit - Just so you don't feel too bad, a P.O. put a grand cherokee (I think) ECM in my 95. At least mines a manual tranny ECM (from wherever it came from) and so far seems to run fine, but my XJ is also a pre-OBD2, so it isn't so quick to throw codes as the later models. I have been considering swapping it with the correct part number (this is why I know the dealer can get you the correct part number - I called them to get mine) but it's not at the top of my priority list at the moment, so maybe I'll do it in the near future.

double_0_7

Called the dealership, got the correct part number. I got lucky because the pick-n-pull had a newly arrived XJ. It had the correct part number ECM for me.

For the first time, I got to drive it with no CELs.

$37.95 for the ECM. Can't beat it.

Thanks guys.

PatHenry

Nice!!! Can't beat that price!

Thanks for following up.

double_0_7

I also asked the guy behind the counter. He said there were four different part numbers, but couldn't figure out what some of them were for.

At least as far as he and I could come up with, the main four for at least my model year, 2000, were based on auto and manual, and federal- and low-emissions.

The ECM I got was out of a fully-loaded cherokee classic, and my base sport without even cruise had the same official part number from chrysler.

Ending in 34AB(at least I think it was AB, but the AB part doesn't matter much anyway. from my time working there, they can't bump from AA to AB unless it's a minor change. If the AB isn't backwards compatible, they have to pull a new part number.)

PatHenry

Considering that the ECM is primarily concerned with emissions, that makes sense that there are only 4 with differences for manual vs. auto and CA vs. Federal. It's easy enough for a modern computer to ignore things like cruise control, but when there are varying inputs (like between a manual and auto due to drastically different tranny operation or between Federal and CA (since CA typically has additional 02 sensor inputs)) it needs to be different.

My 95 definitely has the wrong ECM, but it drives just fine and I get 18-20 mpg without any codes.

Turbo X_J

Ummmmmm, they all do.
If yours is not present or the rubber hoses have rotted, that's the issue.

"And o2 sensor faults when I just replaced them.'
Fuses and associated wiring present and intact for the O2 sensor heater circuits?

double_0_7

According to the FSM and everything else I've read, at least for the MY2000 vehicles, the leak detection pump was only for low-emissions vehicles.

Both the LDP fault and the o2 sensor faults went away with the new ECM.