Hello all, this is my first post to this forum. I recently purchased a 2008 Toyota Tacoma V6 3.0 Liter 6-speed 4x4 and am having issues with the 4WD. It began with the 4WD light and 4LO lights flashing on the dash when the key was turned to the "On" position. I would hear the 4WD ECU click twice, and then the lights would start flashing immediately. When this occurs, there is no response in the 4WD system to the switch being turned to 4HI or 4LO.
At some times when I turned the key to the On position, the lights would not flash. When this occurred, the 4WD system worked flawlessly. It would immediately lock into 4HI or 4LO accordingly, and back to 2HI when the switch was turned back. I could hear both the Tx-case actuator and ADD actuator lock into place, the 4WD green dash light would illuminate, and everything worked great. However, for no rhyme or reason the light would flash at another time (could be later that day, or the next day, no rhyme or reason to it). At this point I thought it could be issues with bad connections in the ADD actuator, so I bench tested and soldered the contact points. Again, it would intermittently work, but most times the lights just flashed.
Eventually I replaced the ADD actuator, but it still did not fix the issue. I inspected the transfercase actuator, and it was seemingly on its last legs. Some corrosion on the contact points and the motor didn't have quite enough power to move the transfercase rod when power was applied directly to the Tcase actuator. I got a used on at a salvage yard that was in great condition. Bench tested proved it worked. I installed it, applied power directly, and it would move the transfer case rod to the 4LO position and back again without issues. However, the light was still blinking. I triple checked that the ADD actuator was in the 2HI position, that the transfer case was in 2HI position, and that the transfer case actuator was in 2HI position. I also confirmed that the position sensors were working correctly, and they were.
I took it to the dealer so they could trouble shoot. Needless to say they spent very little time on it and recommended replacing the transfercase. When they tested at the ECU the TL1, TL2, and TL3 were all showing 12.5 volts of power when the switch was in the 2HI position. According to the pdf attached, this should not be occurring. However, when I test the limit switches at the transfercase actuator they are working appropriately. Not sure if this is a bad ECU, a short in a wiring harness somewhere, or something else. I have not completed the entire testing of the ECU, been short on time lately, but that is my next step (or just replacing it outright). I have a couple of questions:
To replace the 4WD ECU, does it have to be calibrated to the new vehicle when installed? Are there specific models for different Tacoma trucks, or are they generally universal?
Any input on testing the ECU further, or other suggestions of things to look at?
When I apply power directly to the ADD actuator it locks immediately, and when I reverse polarity it unlocks. Same with the Tcase actuator, it goes all the way to 4LO and then back to 2HI when I apply power directly to the pins in the actuator. It seems that everything is in good mechanical condition, hence why I suspect the ECU or a short in the wiring.
All grounds look good. Inspected the fuses and they are also good.
Any help or guidance you can offer is appreciated. I have a lot of hours put into resolving this, and it is starting to really frustrate me. Thank you again.
At some times when I turned the key to the On position, the lights would not flash. When this occurred, the 4WD system worked flawlessly. It would immediately lock into 4HI or 4LO accordingly, and back to 2HI when the switch was turned back. I could hear both the Tx-case actuator and ADD actuator lock into place, the 4WD green dash light would illuminate, and everything worked great. However, for no rhyme or reason the light would flash at another time (could be later that day, or the next day, no rhyme or reason to it). At this point I thought it could be issues with bad connections in the ADD actuator, so I bench tested and soldered the contact points. Again, it would intermittently work, but most times the lights just flashed.
Eventually I replaced the ADD actuator, but it still did not fix the issue. I inspected the transfercase actuator, and it was seemingly on its last legs. Some corrosion on the contact points and the motor didn't have quite enough power to move the transfercase rod when power was applied directly to the Tcase actuator. I got a used on at a salvage yard that was in great condition. Bench tested proved it worked. I installed it, applied power directly, and it would move the transfer case rod to the 4LO position and back again without issues. However, the light was still blinking. I triple checked that the ADD actuator was in the 2HI position, that the transfer case was in 2HI position, and that the transfer case actuator was in 2HI position. I also confirmed that the position sensors were working correctly, and they were.
I took it to the dealer so they could trouble shoot. Needless to say they spent very little time on it and recommended replacing the transfercase. When they tested at the ECU the TL1, TL2, and TL3 were all showing 12.5 volts of power when the switch was in the 2HI position. According to the pdf attached, this should not be occurring. However, when I test the limit switches at the transfercase actuator they are working appropriately. Not sure if this is a bad ECU, a short in a wiring harness somewhere, or something else. I have not completed the entire testing of the ECU, been short on time lately, but that is my next step (or just replacing it outright). I have a couple of questions:
To replace the 4WD ECU, does it have to be calibrated to the new vehicle when installed? Are there specific models for different Tacoma trucks, or are they generally universal?
Any input on testing the ECU further, or other suggestions of things to look at?
When I apply power directly to the ADD actuator it locks immediately, and when I reverse polarity it unlocks. Same with the Tcase actuator, it goes all the way to 4LO and then back to 2HI when I apply power directly to the pins in the actuator. It seems that everything is in good mechanical condition, hence why I suspect the ECU or a short in the wiring.
All grounds look good. Inspected the fuses and they are also good.
Any help or guidance you can offer is appreciated. I have a lot of hours put into resolving this, and it is starting to really frustrate me. Thank you again.