4WD operation

Hello, I am a new member (but not new to Tacoma World). I have been battling the blinking 4x4 dash light for a while now & haven't completely solved the issue. All the threads I've read are great & I learned a lot. Let me know what you think about this situation. The system will engage 4wd high & 4wd low if I move the selector switch in position prior to turning the ignition on. It will not do so if I select either option while the engine is running. I know the 4wd ECM resets each time the ignition is turned on. With the ignition on & in 2wd the 4wd light blinks constantly. My thinking is that the 4wd ECM must be bad. I know the actuators are good because they work just fine. Any new ideas out there ? I don't want to spend the amount of money for a new or (hopefully good used ) 4wd ECM.

 

Does the light continue to blink when rolling in 2WD then moving the switch to 4HI? 4HI to 4LOW you want to be stopped and in Neutral.

 

Find the diagnoses thread, how do you know the actuators are good, obviously they aren’t working right. I’ve NEVER seen the 4wd ECU go bad so im doubting you’ll need one of them.

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

 

I suspect a limit switch is out of range.

Check your limit switch voltages as outlined in the thread below and post your results so we can see where to start looking.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

Well like I said, everything works fine if I move the selector switch prior to turning the ignition on, that alone tells me the selector switch & actuators are operating as they should & there are no shorts or grounding issues. I've done all the diagnostics that are posted, with positive results. I do PC builds & have seen circuit boards go bad for no apparent reason without warning all the time. That 4x4 ECM is just a circuit board in a plastic case. To answer TA2016 If I move the selector switch to 4 high turn the truck on, I am in 4 high and the light stays solid. If while driving I switch back to 2wd the light starts blinking again & I'm in 2wd. Again my 4wd works but only if I select 4wd (high or low) prior to starting the truck which is when the 4wd ECM resets itself. If there was an issue with the limit switches etc. I don't think I would have 4wd in any instance.

 

So your 4wd light is always flashing in 2H though?

 

Yes always flashing in 2wd

 

So check your limit switch voltages in 2H, I bet you will find one is not where it belongs.

 

OK, I will double check that when I get a chance and let you know, Thanks

 

My suspicion is you have a high resistance connection and with battery voltage only the ECM is not seeing enough voltage to make up the logic but while the alternator is on it’s enough to overcome the voltage drop.

not saying the board might not be bad but I’ve never seen one go bad and your symptoms are similar to many others and the PCB was not the solution.


Edit: I can’t spell suspicion