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Discussion Starter #1
I am stumped, having though with my H4 and L4 and suspect it's the ADD unit.

Fuse 31(FWD/Diff) is good but system never engages when shifted to 4X4.
Should the shift fork slide easily by hand from locked to unlocked on the ADD?
Also the vacuum is routed up to the engine bay drivers side but it is capped off. Shouldn't there be a vacuum switching valve or was that only on the older models? Any clue as to why someone cap off the vac line to the ADD?

Please help, I'm on stands in the garage and can't make it to the dealer to look at another FJ and haven't found anything on the internet.
 

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Discussion Starter #4 (Edited)
Switch in the t-case. That's my guess.
there are 3 on the TC right? what should i check other than to make sure they are plugged in and not corroded?


There's no vacuum line to the ADD actuator, only a vent from the actuator that should be connected, else you will get water in the actuator motor and ruin it (ask me how I know). Like FJinCO says, check the 4-high sensor switch in the transfer case first, then the ADD. If you need to tear into the ADD, here is an article I wrote that tells how: http://www.fjcruiserforums.com/forums/how-technical-articles/91004-front-differntial-actuator-repair-replacement.html
thanks for the inside shot of the ADD 1911! definitely not going to move by hand.
 

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Discussion Starter #5
Is there a connection between H4 and L4 sensors? Seems odd that both would go bad at the same time but stranger things have happened.
So close yet so far, however I did service both diffs with Amsoil 75w90 and got to learn a lot about the FJ.
Just so the day wasn't a total loss I manually locked the front diff collar when I had the ADD out. I just couldn't go without seeing those front wheels spin.
 

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Discussion Starter #6
No luck with the H4 sensor. took it out and cleaned the connector then cycled the spring loaded ball bearing.
Do these really go bad that often? I vaguely remember seeing someone post about converting it to a cabin toggle switch.
In any event it is back at the dealer for service, as far as I am concerned it was faulty when purchased and it is their responsibility to fix it.
 

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No luck with the H4 sensor. took it out and cleaned the connector then cycled the spring loaded ball bearing.
Do these really go bad that often? I vaguely remember seeing someone post about converting it to a cabin toggle switch.
In any event it is back at the dealer for service, as far as I am concerned it was faulty when purchased and it is their responsibility to fix it.
Did you test it with an ohmmeter? It's just a simple switch; it should show continuity (no resistance) when the spring-loaded pin is pushed in and no continuity (resistance) when the switch is at rest.

If it's still under warranty, by all means let the dealer diagnose and fix it.
 

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Switch in the t-case. That's my guess.
That's what happened to mine. It cost $145.00 to have it cleaned. I guess you need to "exercise" your 4WD about once a month according to my technician to prevent this from happening.
 

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Discussion Starter #9 (Edited)
Did you test it with an ohmmeter? It's just a simple switch; it should show continuity (no resistance) when the spring-loaded pin is pushed in and no continuity (resistance) when the switch is at rest.

If it's still under warranty, by all means let the dealer diagnose and fix it.
Good to know, I did not test resistance.

My FJ is out of warranty by 500 miles but the purchase was pending a clean bill of health which I had the dealer put in writing. The vehicle was a trade at an Acura dealer which is where I took it for repair, they in turn sent it to their Toyota service.

The pre purchase inspection was performed by the Local Toyota dealer who didn't catch it either but they have offered to make it right in the event that the Acura/Toyota techs do not.

I can fix it but don't feel like I should have to based on principle.
 

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Discussion Starter #11
Well the dealer doesn't seem to want to listen to my suggestions about the TC switches and is leaning towards installing a new ADD. I'm pretty sure it is not the problem based on several threads from the forum. Plus I personally had it off this weekend and it looked good.
 

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1. Test the T-case switch(s) with an Ohm meter in H2/H4
2. Test each connector wire with a volt meter for either ground or power, which ever or if both activates the front drive.
3. Test the front drive connector for both Ground and Hot.

This will determine if there is a lack of ground lack of power, a bad switch or bad actuation motor.
 

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Discussion Starter #13
1. Test the T-case switch(s) with an Ohm meter in H2/H4
2. Test each connector wire with a volt meter for either ground or power, which ever or if both activates the front drive.
3. Test the front drive connector for both Ground and Hot.

This will determine if there is a lack of ground lack of power, a bad switch or bad actuation motor.
Thanks CC. As soon as I get it back I will, provided that they have not already found the issue.
 

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Discussion Starter #14 (Edited)
Well it turned out to be the ADD and not the switches after all. For the record it was around $680 with labor. After seeing 1911's had I been the one to do the repair I definitely would have opened it up vs replacing with a new unit but since the dealer picked up the tab no biggie.

Thanks for the help everyone.

Here is a quick shot in L4 with the locker engaged. w00t!


Now that this is behind me I can move on to more important things like suspension and bumpers, cant wait.
 
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