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Centre Diff Lock won’t engage


Active Member
Jun 20, 2021
Country Flag
Just wondered if anyone else has had this issue?, I was trying to get the front and rear lockers to engage today as I wanted to check everything was ok before it goes in for front axle and diff work, the front diff apparently needs to be locked to be able to remove it so I need to engage the locker.

I don’t have the centre diff lock button so it should engage in low, but when I put it in low the centre lock isn’t engaging at all, I had a brief look online and believe I’ve found the sensor on top of the transfer box, I unclipped it but didn’t undo the sensor going into the box, I will probably do this tomorrow.
Is this the most likely cause?, I’ve read it can be the low range sensor too?.
Does anyone know the part number from Toyota for the sensor on the transfer box?.

All 3 diff locks were working last week when I test drove it, so I’m scratching my head a bit here.

Just ordered the sensor/switch that goes on the transfer box, if anyone else needs one don’t bother ordering one of the expensive ones, it’s the same as a reverse light switch for lots of Toyotas and is a lot cheaper to get, I paid £13 for it just now on eBay.
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..... and ideally on a loose surface so all wheels can rotate differently to ease lining up
As above really, first check the orange light for the centre diff is illuminated, note this is not part of the test light system when the ignition is switched on. Have someone hold one wheel steady and you or somebody else rotate the other wheel forwards and backwards this will allow things to line up, check all three differential lights are on and not flashing. Switch off the differential switches and check all wheels rotate freely and all warning lights are out.
There are 2 sensor switches involved. One detects low range to trigger CDL locking (if you haven't added a dash switch and the pin 7 mod) and the other detects when it has locked. Very little movement is needed for the centre diff to lock. An easy check is to turn the ignition on but don't start the engine. Put the transfer box into L. Do you hear a motor running? Does it run again when you change back to H? The motor runs and winds up a clock spring regardless of if the CDL is in the right position to lock, and then when it is in the right position, will click into place.

When you get CDL working, the rear has quite a course tooth arrangement can take quite a lot of differential movement between the two rear wheels to engage. The front has quite a fine tooth arrangement and should take very little differential movement between the two front wheels to engage.