My 2007 Tacoma's 4 wheel low red light blinks once every one to two seconds. I can put the truck in 4 high and the green light stays on, I can also put the truck in 4 low and the red light stays solid. When I go back to 4 high or 2wd the red light for 4 low keeps flashing. It started randomly when I wasn't even using either 4wd. Also, began to hear a creaky noise like an old rusty door hinge crossed with a clicking noise at low speeds (under 10mph), especially just starting to move or stopping. Both issues may be related. Any ideas?

 

There are a couple of sensors on the transfer case. One indicates whether it is in 2wd or 4wd, the second one indicates whether it is in high range or low range. Seems to me that this sensor (high/low) is failing to UNREGISTER the state of low range.

The sensor is active-low/inactive-float, which means that when the transfer case is in low range, it connects the ecu input (L4 / 17(B)) electrically to the negative terminal on the battery. When it is in high range, it leaves the input to float (low current positive 12v).

What this tells me, is that either you have a broken wire that is shorting to chassis (if it was just broken and not shorting to chassis, it would imply being in high range, which does not describe your issue), or the sensor itself has failed. It is also possible (but unlikely) that you have a failure in the 4WD ECU, the Skid Control ECU (if equipped), or the ECM, or the wires/junctions connecting any of these units together.

If you find the electrical wiring diagram, you can find this switch labelled as "T3 Transfer Indicator SW (L4 Position)" on page 355.


It *might* also be possible to be having a failure in the transfer shift actuator assembly or its three connections to the 4WD ECU, but I believe that it will actually lock out transfer shifting if that is the source of the problem.

Or maybe not... The L4 position should tie TL3 input to battery/negative, leaving TL1 and TL2 floating. H4 position will tie TL2 to battery/negative (other two floating), and H1 position will tie TL1 to battery/negative (again, other two floating). There are two transitional inputs where TL2 and TL3 are both tied to battery/negative (indicating a transition between H4 and L4), and another with TL1 and TL2 negative (indicating a transition between H2 and H4).

The only way that this indicator switch could cause the problem you are describing, is if TL3 is broken and shorted to negative. However, this would mean that the shifter will keep going until it senses the impossible state of all three inputs being tied to negative when it reaches the transition between H4 and H2.

I think that it *has* to lock out if it reaches an impossible state, otherwise it would have to seek around for a state it will never reach. You describe the transfer case *function* to work correctly.

Note that because of how the transfer shift actuator assembly's switches are constructed, it is impossible for that switch itself to be the cause of this problem.