New member Really need help chasing 4x4 issue!!

Hi all,
I just found tacoma world and it seems at the same time my truck ('05 4.0 SR5) seems to have realized that and has been having constant annoyances. The one that I cannot figure out and really need help with before I just start throwing parts at it is with the 4X4. The chasis light and 4lo light blink everytime I drive. Its consistently inconsistent sometimes it starts blinking right away and other times it take awhile to start.
When its not blinking the 4x4 engages and locks up and disengages easily with no issues. It starts blinking and then I cant do anything. Truck hasnt been abused or wheeled just pulls a boat on occasion and hauls all my tools. It was my grandfathers and looks like it just about came out of the factory last year.

SO Ive search and did the front ADD solder fix which it didnt need but did it anyway and sealed.
I then dropped the transfer case actuator and that was also ok with no corrosion. They both work obviously when the lights arent blinking.
Also pulled the fuse and reset the system and that seemed to keep the lights off for a bit but they ultimately came back.
Pulled the position switches out of the transfer case as well and they looked in ok shape (not that i can find the parts numbers to replace anyway).
I am at a loss and really could use a hand on this one. I really dont like throwing parts at stuff especially when theyre not so cheap and quick to get. I will be SOOO appreciative of any additional info on this.

 

You're going to need proper wiring and signal flow diagrams to start with (Mitchell's D-I-Y is only about $50 for a three year subscription IIRC). Then, once you've got those, wait until you have the fault present and start checking each component and the wiring between them. You'll need a DVOM and an incandescent test light. It's very likely that you've got either a bad ground or a corroded conductor or connector, but it may be challenging to locate simply because of where the wires run.

 

2Hi to 4Hi, the light will blink while the system is engaging. Once engaged it will be steady lit. If blinking, then the system is not engaged.

4Hi to 4Lo, will not engage unless you come to a complete stop and shift the tranny into neutral. The light will act similar as before, blinking = not engaged, steady = engaged.

You can verify the procedure in the Owner's Manual.

 

Yeah I know that thanks, Let me rephrase, the lights will start blinking on their own with no influence from me. Also if anyone has the part numbers for the position switches on the transfer case that would be great too

 

So you are just driving along in 2HI and those lights start blinking? What is the "chasis light"?

 

This is important to know. No need to throw parts at until you know where to start.

 

Yeah thats what happens 9 times out of 10 just putting along and the lights flash out of nowhere. The "chasis" light is the 4wd light that I brain farted the name for. that light and the 4lo light both flash together.

 

Just in case anyone else is in the same boat the following issues have also presented themselves which all seem to be correlated...
Cruise control stops being able to be turned on when 4wd lights are flashing
codes for the charcoal canister and vapor pump going bad trip
when I plug a scanner into the OBD terminal with key on and engine off (proper procedure) it appears to ground the comm loop and everything functions as it should.

Im going to investigate the in cab grounding cables and if all else fails add a new ground line off of the OBD terminal either chassis or signal a few inches behind the connector. Determining which will work by using a little jumper out of the front of the terminal first and then moving to permanent behind.

I will post the solution in this thread should I actually manage to get it wrangled.

 

This might help you.
Let us know if you figure anything out.
http://www.automotivetroubleshootingsecrets.com/2008_Toyota_Tacoma_network_protocol.html