Troubleshooting 4WD dash illumination with Atlas 2 install

sierradmax

sierradmax

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I'm troubleshooting why my 4wd dash light isn't turning on after an Atlas 2 install in my 05 Rubicon. I spliced in Advance Adapters 300378A low range switch which states it "Will not light the 4wd dash light in 4 high" but will illuminate in 4 Low. I figure this probably has to do with the fact that the "low range switch" threads into the back side of the front axle output shift rail. As the front axle lever is moved forward (into low), the rail pushes back into the case and must close the switch. Based on my factory wiring schematic, it appears the factory switch completes the circuit or closes the loop to enable a dash light via PCM. So, I unplugged the sensor and tried jumping the wiring (brown - white / dark green- dark blue) to see if I had a faulty switch.. Nothing. Prior to the Atlas install (with the 241), it worked flawlessly.

https://www.advanceadapters.com/pro...er-tjjk-atlas-low-range-switch-kit-1997-2011/
 

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I would try the switch installed and switch it to 4low and see if it grounds out to complete the circuit. Remember there is going to be no voltage at the connector from body harness as the circuit is looking for a ground.
 
motomick76 said:
I would try the switch installed and switch it to 4low and see if it grounds out to complete the circuit. Remember there is going to be no voltage at the connector from body harness as the circuit is looking for a ground.
Click to expand...
Did that and I unplugged the sensor and jumped the terminals on the harness to see if it would illuminate. I realize there is no voltage just a signal (dark green/dark blue) and a ground (brown/white).
 
Ok, when I did my 241 conversion I had to get a different switch. I verified the switch by putting it in 4wd, and at transfer case switch make sure it completed the circuit and went to ground with ohm meter. Want to make sure the xfer case is completing the circuit at the switch when in 4wd.
 
Or you can take a spare piece of wire, and at the body harness connector near xfer case and go straight to ground and verify it lights up at connector
 
hey guys, I’m new here I was just scrolling through the threads and seen this. I recently purchased a new to me 05 rubicon and before replacing a “bad” 4x4 switch I removed it and hit it with some contact cleaner. Put my meter on the switch itself to check resistance (after researching I found the rubicon switch goes off of resistance and not a closure, so the jumper wire test would not work on in this case) and meter was not reading properly as the numbers were jumping around. Resistance changes when you have it on 4 high vs 4 low - contact cleaner helped, resistance reads began changing properly, reinstalled the switch and haven’t had the problem since, it’s been a few months since I did this. I don’t remember the reads but with your switch off you should get a resistance, then with the switch pressed half was down (4high) you should see a change in resistance - press the button all the way down (4low) and read should change again.
Hope this helps.
 
I appreciate this. The Advance Adapter low range switch kit comes with a 62ohm resistor. I had AA called several weeks ago questioning its need as my Rubicon has the Greg method "locker bypass". I was told that the resistor is not needed to make the lockers function but perhaps it's needed to illuminate the 4wd dash light function.
 
So, the resistor was installed and the light still won't illuminate. Yesterday, I called Advanced Adapters and I received conflicting info about prior agreement. I was told it needed to be installed. The above pdf file shows the "offroad package" (Rubicon) transfer case signal as brown/white and the ground as dark blue/dark green (spliced among other sensors). This runs along to pin 26 at PCM connector C2. I have continuity between db/dg and chassis ground. I'll check the signal to pcm C2 later today.

My next approach is to check the instrument cluster 4wd light. Perhaps it went south between the 241 and Atlas swap? However tracing this revealed another question. Instrument cluster C2, pin 11 (violet/light blue) is the 4wd signal for the "offroad package". I cannot find anywhere in the service manual how or where this originates. There is no wiring schematic for the "body side" to this wiring. There is however a "4wd dash light" schematic for the non-offroad package.... The only "offroad package" wiring schematic for the instrument cluster included the lockers.

C2 pin-out.jpg


p725 cluster.jpg


P729 cluster.jpg


p730 cluster.jpg
 
When t/s I always start at 'What has changed' and verify, and it seems you have done that. Good that you are checking the bulb, and follow KISS methodology.

Keep tracing it out, I have noticed that they will bundle two different diagrams on one page, when I was tracing all of the wiring for my swap and dash change-out.

I would stick with the off-road package wiring schematic.
 
So, here's an update. For starters, HouTJ90 is right, the OEM Rubicon 4wd switch "system" operates based on resistance.

I performed the gauge cluster test to confirm the 4wd indicator light bulb wasn't burnt. In fact, it wasn't. A couple of philips screws, and I pulled the cluster out from the dash. The pin-out of the female side of connector "C2" DOES NOT have a wire at pin 11, although the manual says it does have one for the "offroad package" (Rubicon). The cluster was displaying "Open Bus b0" which prompted a DRBIII scan tool. A scan on Saturday yielded two codes (didn't throw a CEL), which were low and high range 4wd open switch circuit. If memory serves me, P0838 & P0839.

I cleared the codes and oddly enough, the 4wd light would come on whenever the front gear shift lever was in low or high. After two "engaged positions", the light would not function no matter what position and codes would appear again.

With the long holiday weekend, I waited until Monday to call Advance Adapters. I was basically told that I needed a "JK Atlas Control Module", P/N 300377A. A websearch on Advance Adapters site & damn... $260. But as I read into it, there was a clear explanation as to how our TJ Rubicon 4WD switch system works with the PCM. I do not know how the cluster light up but it must send a signal (PCI Bus wire?) to the cluster...

To properly understand how to trouble shoot you will need to know how things work. On 03-up TJ/LJ Rubicon models and all JK up to 2018 the factory low range switch is a variable resistance switch. When the transfer case is in 2WD High Range the switch reads about 1100 Ohm’s of resistance/4WD High Range resistance= 670 Ohm’s/4WD Low Range resistance = 62 Ohm’s. Since the Atlas only offers open/closed switches for 4wd and low range a control module is needed. The function of the control module is to provide the correct resistance to the Jeep computer for the different shift positions.

While I know which front gear selection I'm in, and my lockers have been bypassed, I'm told if I want the 4wd light to come on, the JK control module is needed. I suspect that if an atlas is installed with the factory wiring for the lockers, it would be needed, too as without the kit, the "4wd open switch circuit" code would continuously happen, disabling the locker function.

https://www.advanceadapters.com/products/300377a--jk-atlas-control-module/
20201230_192408_resized_1.jpg
 
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