Center Differential Lock Not Working in Low

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My center diff is not working when I put the truck in low. It was just working The CDL only works when the switch is activated and engages quickly.

I searched the threads and performed the following based on what was recommended, but no luck. [The link to the FAQ on Slee is dead]
-- I exercised the H-L shifter about 25x and still no light or click from the kick board.
-- I tapped the T-Case with a hammer, no luck.
-- I tapped the actuator gently with a wrench around it.
-- I put the truck in low and drove around making figure eights on a dirt road.

I haven't jumped the actuator switch circuit yet. Question is, since the CDL locks when the switch is activated, does this mean the actuator is OK and I don't need to jump it?

Thank you in advance I always appreciate the help. I know this topic has been beaten down, but I think I'm missing something before I purchase a new actuator.

Dan
 
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Sounds like someone may have done the pin-7 mod.
No. The truck came from the dealer with the dash button. The PO/OO never made a single modification to the truck. The CDL locked previously as soon as it went in to low gear. I don't know why it's not working now.
 
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I would check the L4 position switch on the t-case. It is similar to the position switch for the center diff lock.

 
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I would check the L4 position switch on the t-case. It is similar to the position switch for the center diff lock.

OK. That was my question. The actuator switch (L4) is different from the switch for the diff lock button switch, I didn't know that. OK, I will try the jump test on it. Thank you.
 
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The L4 position switch is how the ECU knows if it is in "low" range or not. If that switch is not working, it won't engage the center diff lock when the shifter is in low range because it thinks it is still in "high". The other position switch on the transfer case tells the ECU when the diff lock is engaged, and lights up the diff lock indicator bulb in the dash.

The pin-7 mod disconnects the L4 switch input so that the center diff is NOT automatically locked in low range, but is only controlled by the CDL dash switch.

The L4 switch also controls which shift table (H or L) is used for the transmission, which is why the pin-7 mod surgery is done at the diff lock ECU, not at the transfer case.
 
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80t0ylc

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@dpeshkin - What year is your 80 series? '91 & '92 came with CDL switch from dealer. They also did not engage the CDL automatically in lo range. Also had no VC in the T/C.
Edit: I stand corrected on the automatic engagement of the CDL in lo range on the '91 & '92 yrs.
 
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93 didn't have a CDL dash switch from the factory since it turns off ABS, it must have been added by the PO.
I thought so as well. But I asked the PO and they made no modifications. The dash switch is also referenced in the 93 owner’s manual. I’ll take a pic.

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80t0ylc

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Incorrect. All US spec 80 Series automatically lock the center in low range in a stock configuration.
This makes absolutely no sense. If this is true, I have even less respect for Toyota 80 series electrical engineers. If the manufacturer provides a CDL switch to control T/C lockup, why do they want to force you to lock the T/C in lo range? So you're saying that '91 & '92 owners need to do the pin 7 mod to gain full control? Never heard that before, not even sure those years have a pin 7.
 
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This makes absolutely no sense. If this is true, I have even less respect for Toyota 80 series electrical engineers. If the manufacturer provides a CDL switch to control T/C lockup, why do they want to force you to lock the T/C in lo range? So you're saying that '91 & '92 owners need to do the pin 7 mod to gain full control? Never heard that before, not even sure those years have a pin 7.
The FJ80 had the CDL switch to enable the driver to lock the center in high range. Remember, it came with 3 open diffs. The FZJ80 had a viscous coupler in the center diff, so apparently the engineers felt that it was sufficient for 99% of situations. After daily driving both for many years I tend to agree.

On the FJ80 all that's needed is to remove the low range sensor plug off of the transfer case. This gives you manual control of the CDL in L and H.
Alternatively, you can ground pin 7 of the CDL relay and this will give you manual control as well. However removing the plug on the transfer case is completely non-invasive.

The difference between a pin 7 mod on an FZJ vs. an FJ is the transmission shift points. The FZJ has an electronically controlled transmission. In low range the shift points change. The A440F in the FJ80 is hydraulic, so it doesn't care what you do.
 
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