4 low light flashing

2006 TRD. 4 low light started flashing while driving down the freeway. I am finally working on fixing it and wanted to start troubleshooting at the actuator plug so that i could tell if it was the actuator or something upstream. Attached is the pin out of the 6 pin plug on the actuator. The pinout is the same regardless of If it's running vs key is only "on". Also the same regardless of if 2wd or 4wd is selected. My issue is that of course, I don't have any schematics and don't know if this is good or bad. any help?

 

That looks like connector EC1 which is the sub harness that goes to the ADD Actuator, being the L4 light is flashing we're likely dealing with an issue at the Transfer Case Actuator but we need to check things at the 4wd ECU.

Is it beeping as well or only flashing the light?

Things are best tested at the 4wd ECU with everything plugged in.

If you can check your limit switch voltages as outlined in the thread below and post your results we can see where we need to go.

https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

Compared to the expected voltages in 2wd, everything matches except the DL1(B13 light green) is 12V, and the LO(A15 blue) is 0V. In 4H none of the signals change whatsoever. I'm not really understanding the correlation between the two signals that don't match??

 

So it would seem we have an issue in the ADD Actuator or the wire to DL1 is open.
Go to the actuator connector and unplug it, check Pin 6 (Light Green), it should have 12v.
If it does then your issue is most likely in the actuator, if it doesn't then you have a broken wire.

It's interesting that it looks like the 4wd switch isn't working properly either (LO is 0v with the switch in 2H).

When the system sees a discrepancy in the limit switch signals it shuts down all shifting until the fault is cleared and the key is cycled.

 

So it is not seeing coherent position data between the 2 limit switches so it quits sending any signal to the 2wd/4H switch because it senses the limit switch issue? That makes sense, just asking to be clear

 

It doesn't disable the selector switch signals but it disables the actuators from moving when it sees a discrepancy in the limit switch signals if that makes sense.

 

Just verified on my test setup the if DL1 is open in 2H both lights flash rapidly.