2005 TJ Wrangler - No Bus Issue, intermittent no start

[skeletonbobo]

Hi All,

Does anyone have anything to suggest to fix a no start issue with a 'no Bus' code on the dash intermittently.

Symptoms are as follows:
- Intermittent 'no bus' on dash
- Gauges don't work or intermittently work for short periods
- No crank or crank, start, run for two seconds before immobiliser kicks in intermittently

I've tried cleaning connectors on back of dash and I have tried cleaning connectors on computer, battery has charge.

Thanks in advance.

[Fishframe]

This BUS issue is a PITA and will likely drive you crazy.

It is an electrical connection on a module somewhere. Notice I said ‘somewhere’ !

In your case it ‘could’ be the SKIM module or your ignition switch.

The usual way forward first is pull the dash cluster and remove reseat all connections, do same with ECU/PCM and give connectors a clean with circuit board cleaner, even clean and check battery terminals ect…

Then I would go onto the SKIM module.

I read on one forum the issue was connectors to O2° sensors so you can see how wide this could take you.

[skeletonbobo]

It's such a lovely thing.

After getting my car towed from work after my gauges went dead and it wouldn't restart I tried all the internet fixes, cleaning connections, adding dieletric grease etc only to have the same issues reoccur within about 30 seconds of starting it again.

I let it sit for a couple of weeks then started it and ran it at idle on 4 separate occasions for a good 20 minutes with no issues. I then took it around my estate for a good 30 minutes without issue so I was growing in confidence despite still being more or less convinced the problem would return.

Monday just gone it was raining so I couldn't ride to work as normal and was forced to take the Jeep and about 4 minutes into my journey I hear the dreaded beep and all my gauges go to 0. Fortunately this doesn't kill the car but just means it won't start again once you turn it off, so I got it home and it was a wet ride in for me.

I've had another poke around today focusing on the skim module, given the intermittent nature of the issue and the fact that it effects the serial bus communication between the cluster and the ECU I don't believe it is very likely that it will be anything other than a dry joint somewhere.

To rule out the skim I simulated a breach in proximity between the key and skim module whilst the car was running, this did nothing whatsoever and only became a problem once I turned the car off and then it couldn't find the transponder again therefore immobilising. So I don't believe intermittent SKIM failures would cause this problem but rather just make the car fail to start /run on next crank.

Would anyone have any further advice?

I fear an auto elec will just do the same as I, achieve nothing and the problem will persist, especially since the problem is intermittent and it isn't even present as I write this (just took it around the estate again with no issues). This could be a real money pit if I get professionals involved to chase dragons.

Note in the images attached that the scan gauge also looses connection to data because its readings are frozen from when the issue occurs, this was in face at idle in my driveway after bringing it back home upon failure.

[ajftj]

Been 3 weeks since your last post, so hopefully you've fixed it.

Intermittent electrical issues are a pain, don't bother giving it to an auto elec, you sound like you can find it yourself. It's not a difficult electrical problem, it's a physical problem with the electrical system.

Can you read a wiring diagram, there are downloadable ones on the USA wrangler.com site. Identify the comms wires in the schematic, find which harnesses they travel through, and which inline connectors. Just familiarise yourself with the system and the connections.

Next time you get it to start in idle, progressively bend, jiggle, apply stress to the harness while stationary. You might just be able to zero in on the area. I don't know how long the messages between the modules will need to go missing for before you will get the bleep - this could be some seconds so your physical disturbance might need to be bend it, count to 20, release and move on etc...

Check the ground points physically for the modules you are interested in. I'm sure you pulled and replugged the fuses already. How about those fiddly relays. You can swap them around if they are the same type, maybe you'll move the problem to a different system entirely.

You will likely end up having to do a physical inspection, peel back insulation, trace wiring through. Alternatively if you are capable and can identify the wires in question, just overlay that part of the harness that carries the comms externally (might be a twisted pair). You might get away with going point to point between the two modules over the existing harness. Not pretty, but you can bypass all the joins.

A couple of other thoughts.

Think hard about when it first happened - had anything at all changed, did you fit anything new, did someone else use the vehicle. Did you go bouncing around offroad. Was it outside in these recent extreme rains.

Last thought, unplug that third party digital gauge wherever it joins to the comms on the vehicle.

This would be hours of labour for an electrician, so unless you have a friend you can ply with beer get comfortable in the garage.

Good luck!!