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Discussion Starter #1
Is there a way to confirm full locker engagement on an LJ Rubicon?

Why I am asking is the lights both blink and I got bit of popping from the front, implying NOT fully locked. I did not keep messing with with it to avoid damage. I had not used the lockers in years previously. Yep - sad but true :( So - shut lockers off and put it on my lift and...

Front and rear lights blink and never go solid. Pumps fire and put out/hold 5-6psi. The rear pump cycles periodically - once a minute or two. Chased the rear leak to the fitting or inside the diff (stopped at this point). The axles appear to engage/disengage when hose is connected/disconnected and turning by hand - no slip or pops. When compressor on and dogs(?) are mis-aligned (not yet mated) - rotating a bit causes the pump to restart briefly and axle appears to lock when turning by hand. Front and rear feel the same.

All these things added together say they are probably fully engaged, but how can I be sure other than risking damage, given the reputation for faulty sensor indications?
 

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Welcome to ROF!
I had a friend who’s TJ locker indicator lights were sending misinformation. We high-centered it on purpose to check locker switches compared to what was locked. His issue was a faulty transfer case position sensor. I had the same symptoms with my TJ another time. I put my Jeep up on jack stands to check out mine. Be careful if you test in this way.
All this assumes you fixed the air leak and other things are working. Your reference of a popping noise makes me pause. I’ve never had my 2004 lockers, diffs, or axles pop even once.

Someone with more expertise will chime in soon.
 

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....When compressor on and dogs(?) are mis-aligned (not yet mated) - rotating a bit causes the pump to restart briefly and axle appears to lock when turning by hand. Front and rear feel the same...
That sounds like normal operation. Sometimes it takes 20 or 30 seconds for my OEM front axle to lock (rear axle is a D60 and ARB locker.) If both wheels turn in the same direction when they are off the ground, you're locked.

And welcome to ROF, glad you're here.
 

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Discussion Starter #4
Thanks for the welcome to the ROF, the info and advice!

I will check the xfer case switch if I can get to it without dropping the skid plate (not that ambitious at the moment!) and try being more patient. I think I do get the 4WD light, so thinking that may be OK unless there is more than one.

The time the popping happened I did try weaving a bit but was on a mission (dragging a new fallen tree through my yard) and was able to get it done with just the rear locked - so that is what I did.

Do you know what the diff "switch" actually is? is it a full (zero ohm) contact closure or something else? I jumped out the connector and the light did not go solid. Have read that the control might work on voltage levels, implying it could have a resistor in there for a voltage divider. That would explain why the jumper did not cause it to go solid assuming the case switch is OK. I will put a meter on it, cycle the locker and see what I get, but knowing is better than guessing :)

I will do a search for a wiring diagram and see if I can find one / learn anything from that.

Thanks again!
 

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Thanks for the welcome to the ROF, the info and advice!

I will check the xfer case switch if I can get to it without dropping the skid plate (not that ambitious at the moment!) and try being more patient. I think I do get the 4WD light, so thinking that may be OK unless there is more than one.

The time the popping happened I did try weaving a bit but was on a mission (dragging a new fallen tree through my yard) and was able to get it done with just the rear locked - so that is what I did.

Do you know what the diff "switch" actually is? is it a full (zero ohm) contact closure or something else? I jumped out the connector and the light did not go solid. Have read that the control might work on voltage levels, implying it could have a resistor in there for a voltage divider. That would explain why the jumper did not cause it to go solid assuming the case switch is OK. I will put a meter on it, cycle the locker and see what I get, but knowing is better than guessing :)

I will do a search for a wiring diagram and see if I can find one / learn anything from that.

Thanks again!
My buddy had an ‘06 LJ that had a clicking sound in the front diff. We couldn’t find the issue and it always worked so we figured it just liked to talk back to him.🤓
My oem locker lights will flash at times even tho it’s I know it’s locked. Sometimes just backing up a couple of feet will resolve the flashing.
Lock it, point it, stab it, let ‘er go.
 

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You might want to get under there and man handle your driveshaft u-joints too. I’ve heard those pop when loose and needing attention.
 

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Is there a way to confirm full locker engagement on an LJ Rubicon?

Why I am asking is the lights both blink and I got bit of popping from the front, implying NOT fully locked. I did not keep messing with with it to avoid damage. I had not used the lockers in years previously. Yep - sad but true :( So - shut lockers off and put it on my lift and...

Front and rear lights blink and never go solid. Pumps fire and put out/hold 5-6psi. The rear pump cycles periodically - once a minute or two. Chased the rear leak to the fitting or inside the diff (stopped at this point). The axles appear to engage/disengage when hose is connected/disconnected and turning by hand - no slip or pops. When compressor on and dogs(?) are mis-aligned (not yet mated) - rotating a bit causes the pump to restart briefly and axle appears to lock when turning by hand. Front and rear feel the same.

All these things added together say they are probably fully engaged, but how can I be sure other than risking damage, given the reputation for faulty sensor indications?
Check here for a previous discussion:

2005 LJR - Rear Locker not engaging.. light just blinks

I had posted a test procedure from the FSM for determining if the axles are locking or not.

I'll see if I can find the link to the wiring diagram as well.
 

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For me, a flashing light indicated lack of engagement. Unless something is malfunctioning, driving back and forth a few feet helps them align and get locked in.
 

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Discussion Starter #10
Thanks much for the additional replies and info - I will ping the links a bit later.

Have done a bit more investigating and learned that the diff switches are functioning, they are saying they are fully engaged, and the PCM(?) is "hearing" them. Confirmed through a number of experiments with the diffs locking and unlocking, going in and out of 4L, jumping the signals to the box, etc. Also confirmed that the diffs are now both locking. Could feel the front lock up through the steering wheel as expected, and did a diagonal ditch/uphill test (two wheels off the ground) and it pulled through with no pops or bangs.

My guess it that the front popped before because it was not properly engaged from lack of use, my impatience, or both. After cycling a dozen times, they my be freed up. Why the lights only blink is the only open question.

The wiring diagram (Thanks FLLJ!) says the diff switches are simple - either open or closed, so if it is closed, it is locked. This fits my test results with Jeep on a lift. It also says the xfer case is simple also - either open or closed. Scratch that - the Transfer case switch is 5 position according to the Transfer case section of the manual. The PCM monitors that to know when to enable the Lockers.

So - The diff switches are working, and the PCM is hearing/responding to them. The transfer case sensor is apparently working and the PCM is hearing it too. The switches, pump relays, dash lights, etc are all connected to the PCM.

I have heard that the PCMs are solid, so it prolly is not that. I know mine is. Other than having the P0344 Crank Position Sensor / CE Light / limp mode issue and the 42RLE cold/high RPM hard shift resolved temporarily by disconnecting the battery issue, it works flawlessly... ;)

Anyone know what the (il)logic table for the Locker section of the PCM looks like? Wondering if there is some other condition to check for that is needed to steady the lights. I looked through the PCM/TCM section and there is nothing about Locker control.

Thanks!
 

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Start talking PCM and I’m going into fetal position 😆
What year do you have?
 

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Discussion Starter #12
HA Ha ha.... I hear you.

It is a 2006, 86,000 miles. I decided to go with the automatic in a moment of weakness, not realizing the problems they were having.

Back to the lockers, I have a theory for how the lights are supposed to work based on the digital (on or off) diff switches and the somewhat analog Tcase sensor (it apparently has 5 differnt resistances depending on plunger position). My guess is that when the PCM sees 4L (which it does), the locker switch is enabled. Push the locker switch and the lights start flashing immediately, whether actually locked or not. That happens - I confirmed it by disconnecting the diff switches (to make sure there was no lock signal), going into 4L, pressing the lock switch - the lights started flashing. I then manually jumped the switch wires (to simulate lock), the lights kept flashing (that is the issue). Going out of 4L, the lights kept flashing (which makes sense if the PCM thinks the diffs are still locked). Removing the jumpers and the lights go out. Going a bit further, I learned the locker light will flash anytime the PCM gets a lock switch signal - any range, anytime. That also makes sense as you might want to know before you hit pavement if you don't feel them anyway, especially the front.

If this makes sense - and the PCM is getting the signal from the diff switch - why does it keep flashing? Is there another condition not met or is the PCM at lunch?

Thanks for thinking about it and offering your experience and knowledge. I think I know where it is going - but at least I know the lockers are working now :)
 

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You said your diff switches were good but didn't say you tested them? You jumped the wiring so it tested good but did you put your ohm meter on the switches to verify open and closed. Do you have any resistance through them? If one of them had some resistance that could be enough for the cluster to not see "Locked".
 
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Discussion Starter #14
Good question - Yes - I did test the diff switches (this info is buried above - zero and infinity as desired for the two switch states). When hanging on the lift, the lockers may or may not engage immediately when the pumps fire (may need to rotate a wheel to get engagement or disconnect), so I used a jumper to simulate and control exactly when the signal was there and when it was not. And - even with a jumper it misbehaves.

You did give me a new idea. In looking at the schematic, it shows the diff switches pull to ground. What I have not checked is how good the ground is - just relied on the ground connection through the harness. If it is not a solid ground, the "logic" on the other end may not think it is actually a good (low) signal. Have no idea what the threshold is to achieve a "low" in this system. My thinking is that this not the issue, as the blinking light can be turned on and off by simulating locker engagement, so it is hearing something. See the schematic attached. Question is what voltage (V) is needed for to achieve a "low state". Resistance in the wire, connections and the ground connection between the "instrument cluster" and the ground point can cause this voltage to float up if there is enough and it is transistor logic. If it was relay logic as in the old days, this would be fixed by now ;)

Locker Schematic.JPG
 

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Discussion Starter #15
P.S. - It is interesting that some places in the manuals refer to the signals going into the PCM. This diagram says they go to the instrument cluster. Hopefully, it does go the cluster so that Norminator will not need therapy :)
 

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Lie to me if it does LOL
I‘m actually relieved for you if it is PCM related because you have a 2006. That’s why I asked the year. We’ll cross that bridge when we come to it. You’re already over my head with your circuit troubleshooting, but I like learning it.
You would enjoy a Ham license.
You can call me Norm.
 

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I have a 2006 LJ that had the front locker acting a touch weird - just like you described yours is doing. The switch almost always flashed and sometimes went to a solid indication. The locker was slow to disengage and sometimes popped when it did. I too was alarmed as you described you were. So... when I couldn't take the worry any longer, I bought an ARB. After the ARB install, I was removing the air-line to the factory locker and realized the hose had settled and kinked thereby limiting the amount of air flow the unit needed to function properly. Kinked line limits the air in and I'll assume a kinked line limits the air going out. Bench testing showed the unit working like a charm with an unrestricted air-line.
My suggestion is to try and route a length of fresh air-line and test the functionality. Could be an easy fix. Hope this helps.
 

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If the ignition key is not fully pushed in, the PCM will not get the key signal, and the locker lights will flash when engaged, even if fully locked. Similar to shutting off the engine with the lockers still engaged. The key actuator is a known part to fail also. Too much weight on the key ring can cause the key to pull out slightly. Another note on the key actuator, the cast end can break off, causing the PCM to not go into the start mode. The vehicle will not run if this happens. I carry a spare.
 
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