&$&#ing PO836 returns...

[Adrian D]

In line with Jonny's comment, if the indent arm on the transfer case became worn out it would definitely show different resistances than what the ECU expects.

For the NP247 you should see 389-431 in full-time mode and 57-64 ohms in low range.



The ECU can definitely handle all the modes in the table.

[nudibranches]

Yep all checked as outlined before. And I put in a replacement transfer case from a 120k donor vehicle. My old one had some wear as you identified Adrian, but that wasn't the problem.

I am thinking of putting the car up for sale and outline the issue, it has a lot going for it, totally rebuilt engine (20k ago), new injectors, HP pump, rail etc (insurance, dirty fuel), front and rear lockers, winch, disconnects, two inch lift, etc etc.

It's extremely capable off road and drives great. Overall very good condition.


After six years I think it's time to move on. As mentioned, I am looking at petrol and manual.

If I do sell I will post on the forums and you guys can check it out if interested. : )

[5oclock]

I have had my 2.7 crd go into limp in steep bush before because of that transfer case switch also so I can relate to your frustration. I wonder what JeanLuke came up with? Was it a switch and resistor bypass type setup? I have been thinking about a switch to bypass the sender. I cut a failed sender open and in my case it was a spring that had rusted that was causing it to malfunction and not change resistance when the TC lever moved. I suspect the sender is not sealed well enough to stop water ingress in river crossings.I guess the main function of the sender is to alter throttle response in low range??

[Fishframe]

The smoothness and creature comforts of a new or modern 4WD are admittedly great.

However, I often think there’s an argument to purchase an older vehicle like an XJ for around $5,000, then spend a good $10,000 on it to make it brilliant.

Downside is not as smooth, comfortable, safe(?) or technologically advanced.

Upside is reliability, ease of fixing, unique and extremely capable.

[JeanLuke]

To clarify what I did, it was to diagnose the issue, not to solve it. I disconnected the plug from the switch and inserted a resistor (cannot recall the value but search my earlier posts). It meant I was unable to use low range. I drove the car around like this for several weeks and had no errors. It told me that my problem was the switch itself and not the wiring. The final fix was replacing the switch.

I have been through several of these switches in the four years I've owned my WJ. I found Dorman to be a WOFTAM. Two were dead on arrival. A genuine Mopar one lasted lasted around six months. The one I have now is at the link below, purchased Feb 2020 and still going.

Amazon

 

Amazon

EDIT:
Here's the manufacturer's web site: https://ptautowarehouse.autocaredata.com/items/TCS-64
WOFTAM = waste of time and money

[JeanLuke]

Originally Posted by 5oclock

I guess the main function of the sender is to alter throttle response in low range??

It's much more important than just that, although that is part of what it does...

The NAG1 gearbox does not have a speed sensor on the output shaft. The output shaft speed is back-calculated from the wheel sensors. Obviously part of the mathematics involves the diff ratio and the transfer case ratio. Hence, the TCU needs to know the transfer case position. This is also why adding auto-locker diffs or changing ratios causes the TCU to throw transmission slip errors - it breaks the formulae used in the maths.

[5oclock]

Ok on the speed sensor part,so what did you come up with in any experimenting with switches and resistors?? I was going to just rig up some sort of bypass switch and a couple of resistors so I could manually select 60 or 400 ohms for either hi or low so I could drive home not in limp mode. Any thoughts would be very welcome.