My Grand Cherokee (WJ) Finally STUMPED ME! (HVAC Electrical Issues) 

Been a Jeep guy for 45+ yrs (ya, I'm old). New to WJs when I got my '99. Had a few minor issues that I found the answers to on NAGCA. Everything was working fine for months then my sunroof started opening and closing whenever the engine was on. A day after, the driver's seat was always fully forward when I came back. Climate controls on/off repeatedly. Tested EVERYTHING. Nothing out of norm. So...being a Jeep guy and knowing issues like this are caused by the Jeep gods wanting a good ha-ha at our expense, I did the only thing that I know works. I parked it, rolled all windows down, opened the sunroof, turned on the climate control to full, turned on the radio, lifted the tailgate, left all doors and hood open then removed the battery. Came back 28hrs later, clasped my hands together and yelled *_"F### you Jeep gods!"_* , put the battery back and connected it, started it up and all issues were gone. Never to be had again for the next 3yrs I owned it. When the Jeep gods are playing mind games with you, do the only thing possible. Remove their power for long enough that they get bored with you and move onto another Jeep owner.

I have a ZJ with a similar "on" light. The on light says "check engine," and I checked it, and it was there.

Dude, you saved my a bunch of money and trouble with a video you didn't even make. I own an XJ and watch a lot of your videos but the problem I was having was on my dodge truck with the transmission. Dude, you came to me on a dream, told me it was the output speed sensor and it was, that solved the problem. Thanks man, but please stay out of my dreams.

First off, I AM NOT the guy you want working on any vehicle you are fond of and plan on keeping. Oddly enough I know a gent who experienced some of the problems you outlined in this video, and I know he made multiple trips to a pick a part near where he lives and two major brand name auto parts stores for relays, fuses, etc., etc.. He finally threw in the towel and took it to a well-equipped and staffed garage, that specialized in 4X4s and Jeeps in particular, about 100 miles from his home. It took about twenty minutes for one of the older mechanics (a retired Jeep dealership mechanic/technician) to trace the problem back to the computer and some rather corroded connections to the computer. Apparently, the computer had basically lost its little electronic mind because the connections would kick in under the right circumstances only to fail again shortly thereafter. I know they ended up replacing the computer with a "reconditioned" model and the connections were spliced, diced, and repaired by the Old Guy leading to the 2001 Jeep GC still being in daily service as recently as 2022. Beyond that year I don't know what became of the Jeep. By the way, I was told that unless you actually pulled the computer and closely examined the connections you would never know there was anything amiss. I don't know if any of the above will be worth a hill of pinto beans to you, but I am interested in how you solve all your vehicle problems, big or small, and will continue to watch them all.

My mind goes to lowest common issue to the computer, I'm not a WJ expert and watch you to grow my knowledge of working on My own WJ! ! My power wi stopped working , I figured it was a ground issue and found the broken ground where the wire flexes between the door and the chassis. I replaced it with 2 wires of smaller size as I did not have a suitably large enough wire to carry what I guessed was the load carried by that ground. And I used house electric wire nuts to splice the wires together on the new ground. So far that's as far as my WJ electric skills have had to grow.

Doug when I had to take the dash out to replace the heater core on my 2000 WJ Limited 4.7L with the automatic climate control when I got it all back together I had the same problem. Talk about defeated!! I was soooooooo mad and it was December and I needed HEAT. The whole climate control would not turn on at alll. I gave up brought it to the dealer they told me they had a good wiring diagnostic guy and sure enough they found the problem. There is a power wire on the backside of the fuse box that pulled out when I removed the dash and wasn’t making contact when I reinstalled it. I would get the wiring diagram and go after the fuse box. Good luck on it! This happen to me 5-6 years ago. Still have the Jeep 259K and still going!

Doug, try a Body Control Module or check yours and the wiring to it! My '03 was given to me nearly 6 years ago because of some seriously weird electrical gremlins! Now I'm not only an auto guy but I started very Young in electronics and electricity. Not tooting my horn here, but in all fairness I have learned alot over the years. Back to my Jeep. My friend said come get this thing if you can get it going! The WJ had a new battery, full tank of fuel and cold AC, only issue is there were ZERO lights anywhere, no headlights, turn signals, no inside lights, nothing! But it would start and run...occasionally. I had issues with turning the parking lights on would engage the starter, the wiper switch would turn the radio on and off, and on occasion, my blower fan would kick on or the door actuators would act weird and come on without being "on". This was maddening to say the least! I downloaded the FSM and started pouring thru the schematics and to save a really LONG rest of this already long story, it took me the better part of a year to get it fixed almost completely! That was working on it when I could, between work, family stuff, etc. To start, I found the little wiring harness under the dash that runs to the BCM had many wires melted together. Replacing those wires one by one eventually got most functions good and solid, but I still have occasional issues once in a blue moon with my door locks, windows, EVIC, and couple other misc things will stop working and I learned over much trial and error that there's a certain fuse to pull under the hood for about 2 seconds will reset JUST the BCM and everything will go back to normal, until it happens again. I have learned that nearly EVERY non-engine function goes thru that BCM on these things. I hope you get this issue sorted out, man! I hate it for ya, and am genuinely invested now in wanting to know what your issue is! 😎

From what your describing, id go with wrap on the bcm and wiggle test her. ( move wires around gently ) each time seeing if any changes occur.

All i can say is best of luck. I am no mechanic and am looking forward to hearing about the actual little Gremlins that caused the ossue and how you repair it. I have a 1999 WJ Laredo with 143k, and the 4.0 engine. It has had many issues. Radiator replaced, water pump replaced, radiator relay just replaced a second time. Crank Position sensor replaced which was causing idle and stalling issues, both front hub assemblies replaced, upper and lower ball joint in front, new shocks, etc....list goes on. The great thing about the WJ's is the 4.0 engine at least will run forever. The bad, everything else around the engine falls apart. Still love my WJ.

The first thing that comes to mind it to check the backside of the fuse and relay boxes for corrosion. I don't know if WJs where prome to this, but many GMs where for a while; they were severely rotting out causing all kinds of wacky stuff to happen!

Those WJ will go up in prices in the next couple years

Check wiring that runs from dash to front doors. I had odd electrical problems. I fixed these wires, corrected my problems

I own 1 ZJ and 2 WJ's. The ZJ has never given me a problem that I couldn't solve. On the other hand the 2002 WJ (4.7) has a problem with the alarm. I can't find any information about how the alarm works. If you lock the doors with the door switch or with the key, the alarm will go off when you unlock the door and open it. The only way to shut it up is to disconnect the battery. I don't have the key fobs. Maybe that would solve the problem. Please keep up the great videos. Thanks

If i had a dollar every time something messes up on my WJ I'd have enough money to fix something on it 😂

Doug i feel your same heartache wj are great but as all us jeep owners know the electric nannys on such units are hit n miss on getting good or bad wj.anyhow martin of arizona just put up a recent vid on ecm trouble shooting take a look or talk to him.he is also a wj guru and there quirks.snooky pa❤😊😅😊

I had 2001 wj limited with similar problems. I did a skim delete and still nothing. I found that the wiring harness from the driver's side door to fuse panel had a big red wire with the insulation intact but the wire had a gap that would evidently connect some of the time. I bought the harness from eBay and problem solved.

I knew someone with this generation Grand Cherokee, also a Limited, and he had a very similar issue. I think he wound up abandoning the truck. That was around 2011. He had originally guessed SKIM, although I don't recall if he was able to test that theory. Someone we knew who worked with computers tried to insulate the PCM against heat, but that theory never made sense to me (why would it suddenly be more susceptible to the same heat it'd always been exposed to?)... Many years later, I heard of similar problems on ZJs that were solved by backing out the screws on the PCM...

Sounds like you got a wire that the copper went green or check the pins in the fuse box when plugging the fuse in all most sounds like the same problem with my Wrangler it was the pins in the fuse box

Doing the best that everyone does at diagnosing things over the phone, really the comment section in this case, but as the famous words of Eric O from South Main Auto. Check powers and grounds. Resort back to basics. Aint got power going to it so check and see if it has a ground that gone bad and isn't allowing the power to flow through. My wife has a, funny enough, a red 02 WJ Limited with the 5-45 and 4.7 HO and she also calls her Ruby that if I open the drivers side door, the door light goes out, the memory seats don't work and none of the switches in the master switch work as well. UNTIL I close the door, then power windows, locks and memory seats work. I know Chrysler has a bad rap with their wiring and the WJ's are no exception especially in the wires running in the doors so maybe pull the boots back and check there, because sadly at some point im gonna have to do it even though i don't wanna haha. Aint much but it still one more place to isolate and check, and if no wires for the HVAC run through there then feel free to ignore this entirely lol.

I had to have a mechanic put a new ECU and injectors in my 2001 suburban

Grab a wiring diagram and see what is all on that circuit. You verified power at the fuse box and behind it. Check the wiring diagram for splices and check power there. You may have to dig that wire out of the harness and check for power every foot or so until you find the problem.

Really curious to know if you've found the issue yet Doug. When you do, let us know.

Check the ground wires

Ground issue,or a weak battery, battery connections clean, stupid stuff first, worked for me, look forward to u picks

Get your buddy Erick to fix the wireing

Battery. Disconnect it for a few hours. Or put in a battery that you know is good and strong.

Check all grounds for pcm

Doug, When you looked at circuit diagrams, does the memory function and HVAC controller share any common circuits? Perhaps you've looked at that, but that's where I'd start. Does the WJ have a body control module? If so, where is it, is it possible you have a clogged sunroof drain and its making the BCM wet?

This is actually one of the most easily diagnosed vehicle issues that you will see on RU-vid. The diagnosis?? It’s a Jeep.

Sounds like pcm. Fan blower short behind glove box in pins could've started that. Back to junk yard for prices?

BRUSH AND SPRAY ALL THREE CONECTIONS MALE AND FEMALE AT ecm EVEN THOUGH THEY LOOK FINE

Pretty sure it's an issue with the muffler bearings not getting enough blinker fluid to the flux capacitors. So um ya I got nothin.

Question on jeep 06 commander (love better the junk you know?) typic BCM can be an issue. I had a lot of issues and replaced my ignition switch and I cured the shut off blown motor etc

Onece it was pcm it was doing crazy stuff to all of the jeep like not rolling the windows, not working dashboard, other thing can be bad or broken wire of the front driver door thath make the same ot like the same errors. Check the door first.

I don’t know what it is but it’s not skim. If skim and pcm can’t communicate or something effed with the skim it will start and shut off a second later.

This is not a SKIM issues.. if Skim shuts down for any reason it will not restart for 30 minuets. Also Skim shut down will reset your PCM so it has no codes, stored in PCM. Chase wiring, find out why your not getting power to it, your going to find a broken wire or circuit has tripped a breaker keeping power shut off to unit..

O o o o I got it did you check the fuses 😮 lol 😂 and I was actually going to say did you check the ones under the dash but she did and on my liberty it was the ecu burnt out board 😢 did you check grounds

But did you try unplugging it and plugging it back in?

Update?

Have your tried to Hotwire the control unit to 12v to see what happens ??

Sounds like it needs an LS swap. LOL

I'll be back.

i like wj.

Bcm

I had some similar electrical gremlins in my wj. i gave up and took it to the best mechanic and diagnostic guy i know he tracked it down to a short and banged up ground right where the main wiring harness entered the cab behind the coolant reservoir with the 4.0. Dont know if thats your specific problem but happy hunting.

Order a PCM bud, SKIM delete

🇺🇲🇺🇲Trump2024🇺🇲🇺🇲

Exorcist needed.

Maybe the BCM?

Tipm issues?