241OR Rubicon transfer case switch (4WD light won't come on)

Builder

Builder

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I’m desperate on solving this problem. I may do the locker hack but I really want to solve this mystery first.
My 4wd light will not come on. I have 2 brand new Mopar OEM switches, and neither fixes the issue. If jump the plug and complete 5v circuit to the transfer case switch (p/n 5083138AA) the 4wd dash light comes on and my lockers work. But when I plug into the switch, the 4wd light doesn’t come on even though the wiring and switch test good. I’ve tested both switches and the resistance is per service manual specs. I’m getting 5v from the plug, and again all dash lights work OK including 4wd when I jump it with a paperclip. When I plug into the switch I get a good connection. I’ve unplugged the battery for hours, done the dash test, etc. Everything tests OK until I plug into the switch. And again I have 2 brand new Mopar switches. Ugh. Anyone have an ideas?
 
Looks like you are not making good contact into the plug. Are all the contact points looking good in the plug? Photos might help.
 
I thought that too but it’s got good contact. I’ve even jumped the plug to the switch with wires just to try that. I connect the wires (complete the 5v circuit) and 4wd works perfect. Connect to the switch and nothing.

The previous owner said the computer had to be replaced because of a check engine light for the transmission. He got a new computer and resolved that issue, but I’m wondering if this new computer has something to do with this issue.
 
Some photos...

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So when plugged into the switch, you can't make the light come on by moving the plunger, or only once it is installed it doesn't work?
 
Nope, neither. I can only make rhe 4wd light come on if I bypass the switch by jumping the plug. When the switch is connected but uninstalled, it does nothing regardless if I manually push the plunger (duplicating the position the switch should be in 4L) or even when it’s installed and I shift into 4L. And again i have 2 new Mopar switches that I have tested the resistance on both and verified they are per the specs in the service manual.
 
Builder said:
Nope, neither. I can only make rhe 4wd light come on if I bypass the switch by jumping the plug. When the switch is connected but uninstalled, it does nothing regardless if I manually push the plunger (duplicating the position the switch should be in 4L) or even when it’s installed and I shift into 4L. And again i have 2 new Mopar switches that I have tested the resistance on both and verified they are per the specs in the service manual.
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If the circuit doesn’t close when you manually press the plunger you have a defective switch.
Do you know somebody with a Rubicon and can borrow their switch to try in your t-case?
 
This is a rubicon 241OR. These switches are not on/off, rather they’re variable resistance. The circuit should already be closed (constantly - not on/off) when the switch is plugged. The switch will provide resistance in the circuit depending on what selection the TC is in. When the plunger is all the way pushed in (Position 1), this creates the most resistance and this is when you’d be in 2H. So actually the 4wd light should come on when the plunger is all the out (position 4-5).

It’s not the switch. I have 2 new oem Mopar units and 1 new Dorman switch, and all of them work with the 5 positions of resistance.

23E1B5A5-6C6E-4553-ACE0-381BFC7D5B05.png
 
Builder said:
This is a rubicon 241OR. These switches are not on/off, rather they’re variable resistance. The circuit should already be closed (constantly - not on/off) when the switch is plugged. The switch will provide resistance in the circuit depending on what selection the TC is in. When the plunger is all the way pushed in (Position 1), this creates the most resistance and this is when you’d be in 2H. So actually the 4wd light should come on when the plunger is all the out (position 4-5).

It’s not the switch. I have 2 new oem Mopar units and 1 new Dorman switch, and all of them work with the 5 positions of resistance.

View attachment 121645
Click to expand...
I stand corrected, I assumed it was an on-off switch.

When you have the switch connected to the harness but not installed in the t-case, is the switch body grounded to the t-case while you are testing it?
 
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It's possible that plastic in the plug around the contact points has worn down and when you plug into the switch, it's loose and not making contact as it should. Perhaps try putting 1 layer of tape in this area and try plugging it in switch then check again?

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I guess now you'd be checking the computer, order up some resistors with those values and jumper them to your plug and see what you get on the dash.
 
BryantJT said:
He has ruled that out by running jumpers between the pins and the plug directly.
Click to expand...

Jumpers only prove that the electrical circuit is closed, no? If you have a loose plug then you are not making contact as you should.
 
I’m positive the connections are all good. I’ve even created small blades to push into the plug and connected the switch with alligator clips.

While I did this, I tested the voltage with everything connected. The hot side is 5v with no switch connected. With the switch connected, the voltage readings only on the hot side (no measurable voltage present on the other side) is:
Pos 5 = 0.54
Pos 4 = 1.47
Pos 3 = 2.23
Pos 2 = 2.87
Pos 1 = 3.5

So jumping the 5v plug makes everything work great which leads me to think the switch should put out 5v in position 4 since that is the 4L position. However, my reading a say the switch puts out the complete opposite, meaning barely any voltage in pos 4 and the most voltage in pos 1. Maybe someone that knows circuitry can help me.

I’m not sure what else to test.
 
Mystery is solved. It was the PCM. Evidently the previous owner had installed a new PCM (for a non-rubicon) and everything worked perfect, except the lockers. I swapped a PCM from a 2006 LJR into this 2005 LJR, and everything works. Now I need to find someone to reflash this PCM correctly from the 2005. Thank you for everyone’s help and input! Special thanks to MrBlaine for his wisdom too.
 
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Hello Builder,
I am having a similar but not identical issue. To level set, I have an 06' LJ Rubicon w/ auto trans. I was getting intermittent p0838 codes and the 4WD dash light was also intermittent. I replaced the switch on top of the trans case with an OEM and it did not fix the issue. I did the dash check to reconfirm the 4wd light worked (FYI, the locker lights did not cycle during this, only the 4wd light). My jeep already has a wranglerfix.com pcm replacement. Wiring seems fine, connectors are good.

Any advice on where to look from here?

Many thanks in advance.

Wade
 
Wessels69p said:
Hello Builder,
I am having a similar but not identical issue. To level set, I have an 06' LJ Rubicon w/ auto trans. I was getting intermittent p0838 codes and the 4WD dash light was also intermittent. I replaced the switch on top of the trans case with an OEM and it did not fix the issue. I did the dash check to reconfirm the 4wd light worked (FYI, the locker lights did not cycle during this, only the 4wd light). My jeep already has a wranglerfix.com pcm replacement. Wiring seems fine, connectors are good.

Any advice on where to look from here?

Many thanks in advance.

Wade
Click to expand...

what did you find out [email protected]
 
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