• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

'87 Cherokee (No Check Engine Light?)

Twilightoptics

NAXJA Forum User
Location
Vancouver, WA
New to the XJ thing. Girlfriend bought one to come wheelin with my Wrangler. It's an '87 Limited. Among other problems that I'm eliminating,(broken T-case, broken steering column, ghetto rigged push button start), the Jeep has no provision for a check engine light.

The template is there, with no lighting pod. No ALDL port. No wiring in the harness that goes to the empty lighting pod on the circuit panel.

Is this normal?

It's a 4.0L FI. How does one diagnose sensors and so on?

Thanks
-Paul
 
Welcome to the RENIX (Renault/Bendix) era XJ's....

The 87-90 Models do not posses a way to retreive or store trouble codes, the computer can be scanned using the BRD II with the Jeep adapter, but you have to catch the codes as they happen. That is what the tow yellow capped connectors are for under the hood.....

It's a simple system to figure out if you are good at reading from a book. All you need is a digital Multmeter and some basic automotive knowledge.

Best of luck!!!!

I too own an 87 XJ 4.0L....
 
The Jeep you have is what is known as the RENIX. The Renix does not use a check engine light. In 91, when the XJ went to OBD1, it then started using a check engine light.

With the RENIX, in order to do diagnostics on sensors and stuff, you need a decent multimeter. I have a digitial and it has worked great, but there are a couple tests that would better done with a analog. Search the site for different tests for the different sensors. It shouldnt be all that hard to find.
 
The template was there because the same panel was used (I believe) with the GM 2.8L V6 - which was OBD-I compliant (it was a GM engine used with GM controls.) The 4.0L and 2.46L were AMC engines, and weren't OBD-compliant until Chrysler made them so in 1991.

GN/BN - Good News is that nearly any troubleshooting that wants doing can be done with a DMM (there are a couple of tests that want an analogue meter, so the buffer circuits in the DMM won't interfere with the results. Fortunately, they're problems you're not terribly likely to run into.) Bad News - there aren't many "code readers" that can "talk" to the RENIX controller - the only two I can think of were the Chrysler DRB-II scan tool and the Snap-On MT2500. Both will give you realtime driveability data, but RENIX does not "store" or "throw" codes.

Given all that, I'd take RENIX over OBD-I any day (OBD-II - 1996-up - is an improvement. However, OBD-II was "designed" by SAE, while OBD-I was designed by California - specifically, the California Air Resources Board. California hasn't gotten a damned thing right that I can remember...)

I've owned five RENIX rigs to date, so I've got a fair idea of how they work. If you've any questions, you're in the right place (I've also got a sort of "meeting of the RENIX minds" at groups.yahoo.com/group/RENIXPower. I'm trying to collect tech information there - but please discuss it here. RENIXPower is a low-traffic group, and it's mainly an information storehouse, more than anything else. I've also got some downloadable tech info at my own site - link in sig - in multi-part .rar format. You'll need WinRAR to put them back together, and Acrobat Reader to view them.)

But, most sensors can be handily tested using a DMM and some patience - and most of them are GM parts anyhow, so they're pretty common.
 
poorboy_616 said:
Okay, so what part is Renault? which is Bendix? and which is GM?

The Brain says Bendix, some of the sensors are GM, but what is Renault?

AMC history gets sort of goofy in the early 1980's...

In 1984-1986 (XJ) and 1986 (MJ,) they wanted a six-cylinder engine but they hadn't gotten the 4.0L finished yet. So, they licensed the 2.8L 60-degree V6 from GM until they got the 4.0L done. GM sensors are pretty standard all around - AMC used a lot of GM stuff, most ChryCo sensors are based on GM units, and you'll even find some GM stuff on Fords.

While AMC was redesigning the 258ci six to make the 4.0L, they were partnered with Renault - since they were designing the XJ to be a unibody, they needed some heavy computer time for FEM of the structure to make sure it would hold up. American companies hadn't caught on to the unibody idea yet, so they went to Europe. AMC had partnered with Renault (if you recall, up to about 1988 AMC dealers were also Renault dealers.) Renault designed the framework for the control system, and Bendix/King built it - that's how we get RENIX (RENault/bendIX.) I'm looking at a RENIX ECU built in early 1988, it's got "Bendix" cast into the housing, and "Built in France" on the tag. I've got one stripped out in the shop (no housing,) but I don't recall the markings on the board.

Bendix/King is also known for making avionics (instruments and radios,) which explains the longevity of RENIX controllers. I've heard of three that have failed - I have two. I've also got a stack of "known good" controllers, and two complete working setups (one from a scrapped rig, and one from a conversion that was done.)

Anyhow, AMC rolled out their 4.0L inline six in 1987 (along with a slightly redesigned front end - the front clip is a couple inches longer, and the firewall was modified slightly to accommodate the longer engine block) with the RENIX control system. Historical Note - there is no such thing as a "factory carburetted" 4.0L six - they're all MPI.

AMC/Jeep was purchased by ChryCo in early 1988 (late 1987?) (Lee Iacocca,) and some small changes were made - like ditching the Peugeot BA-10/5 for the Aisin AX-15 (a step forward!) in mid-1989. Going from the 21-spline transmission output/transfer case input to the 23-spline (also a step forward.)

For 1991, the 150ci four and 242ci six were saddled with OBD-I compliant control electronics (a step backwards,) although I'll admit the Chrysler stuff is better than Ford's (and not quite as good as GM - I don't like the "one black box" control setup they use. GM doesn't "integrate" as heavily, and component replacement is more possible.)

In 1996, the 150ci four and 242ci six were made OBD-II compliant with the rest of the ChryCo fleet. ChryCo still stuck to the idea of "one black box" - while OBD-II makes somewhat more sense, I still don't like the "one box" idea.

The XJ was Dx'd after the 2001MY, and the 242ci six ended production at the end of the 2007MY (20-year run.) The 150ci four was also used in the Dakota compact pickup, and I don't recall when it ended production. (The AMC Six family included the 199ci, 232ci, 258ci, and 242ci engines - in that order - and enjoyed something like a 45-year production span.)

"RENIX" was the name for the joint venture (technically between Renault and Bendix,) and it's also the name for the era where the control system was used (1987-1990 XJ and MJ. The YJ had the 258ci six with the carburettor, until that was replaced with the 242ci six for the 1991MY.) The RENIX control system is also "pre-OBD" - which is why it doesn't do codes. Frankly, I don't think it needs to, either.

Factoid - IIRC, when the "Ten Best" and "Ten Worst" vehicles of the last century were listed, the XJ was in the top five of the Ten Best. Three of the "Ten Worst" were Renault. Go figure.

Factoid - The RENIX control system was also used (in a modified form) by Volvo under the name "FENIX." No, I don't know why they changed the name.

Class dismissed. There will be a test next week...:laugh3: :twak:
 
Ahhh... Thank you teacher!!

I fiigured that GM sensors were common, MAP sensor being one of them...

It's nice to know that I don't have to go to friggin france to find parts for the ECM as they only appear to have written the programming for it.....

Also my local wrecking yard has a ton of renix era xj's so a brain should be no trouble to find....


The one black box idea is what my 94 T&C uses, it's good and bad at the same time. If something in the brain fails, it's just one box. But, it's also JUST ONE BOX that costs $400 bucks to replace unless you take your chances at the boneyard....
 
XJ Stryker said:
:worship::worship:Awesome write up 5-90 I didnt know any of that.:worship::worship:

Thank you. Bear in mind that was largely based upon (admittedly sometimes faulty) recall without referring to notes, but I'm sure most of it is accurate (and I'll be corrected if it is not.)

But it is handy that most RENIX control sensors are standard GM parts - since they're the easiest to find, and usually the least expensive (and they probably have the greatest number of variations available. While a standard RENIX MAP is 1-bar, or one atmosphere for a naturally-aspirated engine, I can dig up 3-bar - for up to thirty pounds of boost! - without too much trouble or too much money. And, as I recall, the RENIX programming and fuel maps are "open-ended," since that's the way Bendix/King usually likes to work. I really need to dig in and tear the fuel maps apart one of these days, tho...)

Finding a new brain should be quite unnecessary - as I said, I've only heard of three that have failed worldwide to date, and I have two (one from South Africa, one from San Francisco.) Hell, I've personally replaced a dozen or so different ChryCo SBEC/SMEC/PCM units in a two-year period when I was "freelancing" between jobs. Yet another reason I prefer RENIX...
 
Again great info here My 87MJ check engine doesn't work. I just started checking
wires with the test light today not real sure which way to go next. Don't have a diagnostic
tester to help.
 
Welcome to the RENIX (Renault/Bendix) era XJ's....

The 87-90 Models do not posses a way to retreive or store trouble codes, the computer can be scanned using the BRD II with the Jeep adapter, but you have to catch the codes as they happen. That is what the tow yellow capped connectors are for under the hood.....

It's a simple system to figure out if you are good at reading from a book. All you need is a digital Multmeter and some basic automotive knowledge.

Best of luck!!!!

I too own an 87 XJ 4.0L....


Where is this book you speak of?
 
For posterity: One thing that seems to be incorrect in this thread is that the Renix era did in fact have a "check engine" light that worked. The issue is that, as described below, it was in no way connected to anything that could remotely offer diagnostics ability. Instead (at least on my '90), it was connected to a clear plastic box under the drivers side lower dash. When I inspected the one in my XJ, it appeared to be a one time use timer that would simply trigger the check engine light after a preset number of hours was reached. On mine, the cable was disconnected but when I plugged it in, the check engine light came on. My reading on this led me to believe that Jeep put this in as a trigger for the owner to take their vehicle into the dealer for inspection where they would replace the O2 sensor and install another timer module. I suspect most shops simply changed the O2 sensor and simply threw the timer away.


HTH
Todd
 
For posterity: One thing that seems to be incorrect in this thread is that the Renix era did in fact have a "check engine" light that worked. The issue is that, as described below, it was in no way connected to anything that could remotely offer diagnostics ability. Instead (at least on my '90), it was connected to a clear plastic box under the drivers side lower dash. When I inspected the one in my XJ, it appeared to be a one time use timer that would simply trigger the check engine light after a preset number of hours was reached. On mine, the cable was disconnected but when I plugged it in, the check engine light came on. My reading on this led me to believe that Jeep put this in as a trigger for the owner to take their vehicle into the dealer for inspection where they would replace the O2 sensor and install another timer module. I suspect most shops simply changed the O2 sensor and simply threw the timer away.

Correct. It was a maintenance reminder only.
 
FYI 86 federal emission trucks with the 2.8L had no computer or diagnostics at all. The only electronics under the hood were the ignition module and early fuel evaprorative systems.
 
Last edited:
Back
Top