Mullins_j

I have searched the forum and found many reason why the "no bus" message will display. But I figured I would start a new thread since my situation is a little bit different.

So my GF bought a 2001 XJ for her daughter recently. The seller told us that he had just replaced the motor, since the first motor was seized. Same year motor.

The Gauge cluster shows "no bus" and the airbag, check engine light are on and none of the gauges register anything. I did test the cluster itself and it seems to be working fine.

The thing that makes this a little different is that the Jeep will not even crank over sometimes, it's just random, not even a click. I thought it might have to do with the CPS but I don't think that is the case anymore. I unplugged the CPS and the gauge cluster stayed the same. And the CPS would not cause the Jeep to not crank over, it would just not start.

I did just replace the plugs and the coil pack. I'm wondering if the NSS would cause this issue? I'm going to go clean the CPS and put that back in, then see if I can start it in Neutral.

But this still does not help me with the gauge cluster, I did tear the dash apart and clean the connections to the cluster. That did not seem to work.
When the jeep does start, it runs very smooth and good. Other then not having any gauges.

I also replaced the ground braid between the motor and the firewall, it was not even there.

Any ideas on where to start?
I think my plan of attack is going to be:
1) NSS
2) starter
3) start tracing wires

Thanks,
J

F1Addict

I do not envy you for the task that lies ahead. The NSS won't cause a No-Bus but it can obviously cause starting issues. Are there other signs of NSS failure? Will it start in neutral? Do your reverse lights work?

I hope you got a great deal.

bsmith97xj

5 volt sensor voltage is shorted to ground

CCKen

Do you have a Sentry Key Immobilizer system?

A defective SKIModule will corrupt the CCD Data Bus, causing no instruments, and will cause a no-starter situation.

The SKIM and the instrument cluster is powered from fuse #9 in the Junction Block, which is powered from fuse #3 in the PDC, through the ignition switch (start/Run position).

Mullins_j

I have not played around with the shifter yet. My first jump was to go right for the CPS, but after thinking about it, that does not make sense. CPS does not control the starter turning over.

We got this one for $2500. Very little surface rust and super clean inside. The guy we bought it from said that the new motor only had 80K on it, and the head was rebuilt the the motor was installed.

Thanks,
J

Mullins_j

Ok, what sensors have 5 volts to them? And if I go around unplugging them one at a time, will I see the gauge cluster some back when I find the one that is bad?

Thanks,
J

Mullins_j

SKIModule? How do I know that I have this? What is this? I'm a jeep guy, but I like the pre-96 jeeps, less crap to deal with. I have a '94 that just runs, and has close to 300K on it!

Does this some kind of security?

Thanks,
J

CCKen

The SKI system is a security system common in the 2000 XJ. The module is wrapped around the ignition switch, sorta. It uses a different kind of FOB than the non-SKI system FOB. I think it's gray instead of black.

Mullins_j

The FOB that came with the jeep is black. I have the entire dash apart, so I'll check out the ignition switch next time I get over there.

Thank you,
J

CCKen

Correction to above: The FOB is the same I think but the ignition key is different.



If you can access the SKIM (see pic) and detach the 6 wire black connector (3) from the SKIM (if you have one) while you have no instruments/no bus, and the instrument cluster comes back to like, the SKIM is bad. The dealer has to rekey/program the new SKIM.

Mullins_j

Thank you for that info!

I did go and play around some more. Here are the results:

1) This XJ does not have the SKIS. (Sounds like an STD)
2) Shifting has no effect on the starting, it does not start in Park or Neutral.
3) I did short the starter out to make sure that the starter was still good. All was fine there.
4) I went to the starter relay in the PDC under the hood. For some reason the coil side of the relay is not getting charged, which tells me it's a control circuit that is causeing the issue. I can turn the key to the on position and jump out the starter relay terminals in the PDC and the jeep will start and run fine.

At this point I'm leaning towards a bad ECM. What do you guys think, anything that I'm missing?

When trying to start the jeep I can hear a relay on the passengers side kick panel, but that is it, no click, no crank, no start.

Looking at the wiring diagram in the back of the book, one side of the starter relay is connected to ground, and the other side is connected to the PCM. The side that is connected to ground, is good. I get no power from the PCM side.

Thanks,
J

Mullins_j

I also noticed that I get massive shocks when getting in and out of this jeep. I wonder if it would be worth my while to re do all of the grounds first?

Thanks,
J

CCKen

You could read through this thread and see if any of it pertains to your situation. The diagrams are for a 97 but the 01 is very much the same.

https://www.cherokeeforum.com/f2/no-...issues-165043/

CCKen

Good idea.

CCKen

Here's some images that show the engine bay grounds. They are of a '99 XJ but are the same as the '01. G101 is in the same place as your '01 but of course you won't have an ignition coil there.

If you have a Lowes near you I suggest getting a small tube of a product called NOALOX, made by Ideal. Can be found in the electrical section of the store. Use this on your ground wire ring teminals after you clean them. pic below.

When cleaning the wire ring terminals clean them to a polish using very fine sandpaper, wire brush, etc. Make sure the structural ground points are super clean as well. Apply the NOALOX to both the ring terminals and the structural grond points.

The main battery to chassis ground point is G100. It is a sheet metal screw holding it to the fender. Make sure this ground point is very clean/free of corrosion.

The ground point G102 (oil dipstick tube) are the data link connector wires and are not a primary ground but should be corrosion free anyway.

The firewall-to-engine bonding strap is primarily used in radio noise suppression but does ensure a continuous loop of grounds through the engine/chassis.

G106, by the PCM has lots of grounds there, which are listed in the image.

G101 is the main battery to engine ground and does have some important grounds there, such as the PCM.











NOALOX