[toddmac]

Hi everyone, I need to see if I can get some help sorting out an engine code issue. We recently got the wife a 96 Cherokee Laredo and it's now indicating check engine all the time...nice...
When I broke down the codes it shows 12, 72, 55
From what I am reading here and other places....the 55 is the end of codes and 72 is an issue with the ambient air temp sensor but the code 12 is throwing me fits...I have read it means nothing and also that it indicates a retarded timing issue on bank1. Next I read that anytime there is a code set that the timing is retarded 10 degrees automatically....yikes.
SOooooo Do I care about the code 12? Is it nothing or is it showing because the ambient air sensor is malf and caused a retarded timing condition?
Yeah, I read too much..LOL Sorry, just don't want to pay someone to fix something I can do myself. If the 12 is valid, what is the fix for it?
Thanks everyone! Todd

[leftlanetruckin]

hey todd, welcome aboard.

where are you in Mo? i have the scanner that will tell us what we need to know with a little more accuracy. also have a 96 4.0 we got for our boy that is sitting in the yard, may be cheaper to swap some parts over instead of throwing money at it....

martin

[toddmac]

I'm in Independence, Mo. Yeah I keep thinking I should get a scanner, that's one of them tools that ya use once a year or less (hopefully) but it's great to have around. If you are close to me, so far the only thing I am sure I need is to replace that ambient air sensor, that I think is out behind the bumper. The 12 code, I will see if someone here knows exactly what the scoop is or drag my lazy butt up the road the whooping 2 miles to Advance Auto and get em to read it.

[USMC_XJ]

from personal experience, 12 is that power to the pcm from the battery has been disconnected within the past 50 key on cycles... pretty much if you disconnect the battery or the harness from the pcm.

in my haynes manual, it says 72 is from catalytic converter. probably an o2 sensor.

[blackjack2]

The Factory shop manual for my 96 XJ states the following:

MIL Code 12 = Direct battery input the PCM was disconnected within the last 50 key-on cycles. Just means the battery was disconnected.

MIL Code 72 = Catalytic converter efficiency failure.

MIL Code 55 is a sign off indicating the fault code display has completed it's cycle.

There are six “sub codes” for the oxygen sensor failure under MIL Code 21. For example, MIL Code 21 "sub code" Code P0131 = Upstream O2s voltage shorted to ground. These “sub codes” are called Generic Scan Tool Codes and don‘t blink out on your dash. Only MIL code 21 will blink out. You need a code reader. You can go to Autozone or some other parts distributor and they will pull all the trouble codes stored in you computer (for free). In any case you didn’t mention MIL Code 21 in your post so I assume it‘s just not there.

Your 96 probably has the OBD II system (like mine) which was introduced that year. Older Jeeps had the OBD I system and I’m not sure if they use the same set of trouble codes.

There was an emissions related recall of 1996 XJ’s to replace failing cat converters. The following is copied from the first page of the recall.
August 2006 Dealer Service Instructions for:
Emissions Recall E22 Reprogram PCM and Inspect Catalytic Converter

1996 (XJ) Jeep® Cherokee
1996 (ZJ) Jeep® Grand Cherokee
NOTE: This recall applies only to the above vehicles equipped with a 4.0L (ERH) engine.

1997 - 1998 (AN) Dodge Dakota
1997 - 1998 (XJ) Jeep® Cherokee
1997 – 1998 (TJ) Jeep® Wrangler (built after June 30, 1996)
NOTE: This recall applies only to the above vehicles equipped with a 2.5L (EPE) engine.

Contact your local dealer and you may be able to get it replaced for free like I did.

Hope this helps

[toddmac]

Thanks for all the info! I will get it scanned to make sure I am on the right course and then see about the recall info too. It does have a sticker under the hood with a recall that was performed a year or so back, there's a number on it so I will see if I can trace it down too and see what it was about.
The previous owner also put on a cold air kit....I'm suprised there isn't some emisson related components involved with it...it's just a stainless tube with a filter and the only line is the vent to the valve cover. I have a feeling maybe there should be more there. It does have one more port that is capped off on the tube but I did a lot of digging around and never saw anything disconnected or capped off so maybe all is well. It was installed by the same person that when he removed the stereo amp...well, it ain't pretty. I can tell something is missing..couple of unhooked harnesses under the back seat and the speakers are all crossed up...LOL. It works still but I do sure wonder what used to live where the harnesses are....there is a module of some kind still there bolted to the floor and it's connected....odd what ya get with a used car sometimes.