Finch

Picked up a 2001 Cherokee sport WITHOUT the sentury key security system with the typical "no bus" on dash and no start issue. Sounds like a bad crank sensor? Yea well thats what i thought to... new cps and a used cps from my other running 01 xj and this bastard wont start... then magic.. one day i went oit and cleaned off the easy grounds and it started but still said no bus.. 5 days later now it wont start again. Does anyone know where all the ground locations are or have wiring diagrams of what pins to check for continuity.. this jeep is an absolutle corroded mess and i feel there around ground behind the dash i am missing. And wiring diagrams would be great.

CCKen

Quite often a No Bus is caused by poor grounds in the engine bay.

Open this link and scroll down to post #49. It shows the ground points in the engine bay.

https://www.cherokeeforum.com/f2/gre...e-6558/index4/

G101 on your '01 will look different because you won't have a coil there, but the grounds are there. Be careful taking the nuts off. They're Keps nuts and may be locked in place and when trying to remove the ring termanal nuts they will chew up the wires. Use some penetrating oil before removing. As seen in the pic, G101 is the ground for the PCM.

G100 is a critical ground. It is the primary ground path from the battery to the chassis. The inner fender is usually rusty and you may snap the head of the bolt off trying to get it out. Use penetrating oil here as well. This ground has caused No Bus situations.

If you sanp the head of the G100 bolt off, you can get at the bolt stub from under the right plastic wheel well liner (pic included in post #49). Just use vice grips to turn the bolt stub in towards the wheel well to remove it.

The Firewall to #14 cylinder head bolt is a radio noise suppression bonding strap but is an alternate ground path to the chassis, via the engine block (G101). The firewall under this ring termanal rusts out like G100.

G106 are various circuit grounds and wouldn't cause a No Bus but they are worth cleaning.

Use 3M Scotch Brite pads (gray), or 400-600 grit sandpaper, to scrub the ring terminals clean, and use a motor driven wire wheel or sandpaper to remove the rust from the chassis.

It's a good idea to use a product called Ox-Gard (Home Depot electrical section), or NOALOX (Lowe's elecrical section) between the ring terminals and its ground point. NEVER use Dielectric grease on these grounds.

Finch

Cleaned all the grounds, didnt seem to help. Still have no bus on the dash and the cel pops up after about 10 seconds. (No cel is on when the key is first on) the asd relay is clicking and now the cooling fan kicks on as soon as the keys turned on. I even replaced the negative battery cable.

CCKen

What CEL Code(s) numbers are you getting. If you can get it/them it would be a key to your probllem.

You said the Heep is a corroded mess. Does it look like it went for a swim at some time (high water marks under the dash)? Or in the Power Distribution Center.

With the [radiator] fan kicking on as soon as the key is turned to ON may mean there is corrosion issues in the Junction Block (passenger footwell).

If you can pull the complete cover off the JB and pull the big connector with the bolt holding it on (C4) see if there's any corrosion in it. See if there's any surface corrosion anywhere.

Fuse 9 in the JB powers the instrument cluster, fuse 10 in the JB powers the Radiator Fan.

Check #9. It's the 6th fuse up from the bottom in the front row of fuses.

Finch

#9 fuse appeared good, however i did notice some corrosion behind it the picture shows what i mean about weird corrosion. Ive never seen the spare fuses corrode lol. I have a pin out of the ecm connectors, tomorrow im going to grab a continuity tester and just go down the row of pins.

Finch

We hooked up a scanner and it wouldnt connect.

CCKen

Pull connector C4 and see what it looks like.

Pull some more installed fuses and see what they look like.

Check the Data Link Connector pin cavities and see if they're corroded.

On and On....

Finch

Pulled the white connector on the jb with a 10mm bolt and it looked clean, there is corrosion on the data link pins but i still have power and grounds according to my ****ty test lights. I already swapped ecms with my 01 xj and both computers started my other one. The problem is we had this thing running and the instrument cluster still said no bus, then it just stopped starting again.

Finch

Is there anyway to pull the junction block out of the pass kick panel? I want to see whats going on behind it

PUNISHER

Yes there is and it isn't an easy job to do. At least it wasn't for me being I am 6'2" and 300lbs. I removed the passenger seat to give myself enough room to get it out. It's a small area for sure to work in but, it is doable. If my memory serves me right, there are studs with nuts holding the panel in.

I had the exact same problem you are having and all my issues were due to the XJ being dunked in a mud hole. Not by me but, one of the PO's before me. I changed out the PCM, TCM, air bag module, fuses and so on. The TCM and air bag module were all full of dried up mud so I pulled every plug I could find and cleaned them etc. Long drawn out story for sure.

Anyway, after several attempts and just about ready to give up. A guy stopped by to buy a 242 case I had. He asked if he could take a look at my XJ. Low and behold he found the fuse to PCM blown and once he changed that. It fired right up!! Weird part was that all the fuses were new, changed by me and checked by me and several other people along the way. I hope I don't confuse you with all this but, I hope it may help.

Just remember that anything you do, unhook the battery. The air bag module was the last thing I changed and I may not have unhooked the battery beforehand. Which may have popped the fuse, or it was blind anger getting in the way because I didn't go back and double check..

PUNISHER

oh, one more thing I forgot to mention. I made a phone call to a Mopar technician and explained what was going on. He told me that any faulty module can corrupt the PCM. So that is why I started looking into the TCM and air bag module. Now is the info he told me correct? I honestly can't say.

I can say that CCken is pretty slick and knows what he is talking about. So you are good hands here!

Good luck and keep us posted with your findings!

Finch

Whats bothering me is that i have the cooling fan kick on full blast as soon as i turn the key on. Like its directly conneted to keyed power.

Finch

And thanks for all the help guys i appreciate it. I really dont want to part and scrap it out.

PUNISHER

Yep, the fan cutting on as soon as the switch is turned on is what started all this for me. I even drove my XJ to work and the next time I went to start it, BANG, all heck broke loose!

Finch

The good news is i have an 01 xj that runs great that i can swap parts from.