Possible 4wd ecu issues

Hey what’s up? I’ve been battling the f’ing 4hi blinking light.

so far, I’ve replaced the tc actuator electric motor and the front diff add actuator. Tc works when going to 4hi but nothing from the front. Pulled the new add actuator off, bench tested without issues.

Electrical isn’t my strong suit but found there are no power. Coming to the electrical for the add actuator. Chased the wire up hoping to find a short but nothing. Checked fuses, relay, etc with nothing. I’ve got two very young kids so my time is really limited ended up bringing it to a very reputable and trustworthy shop.

the tech checked actuators, agreed they’re not the issue. He then chased the wires up through two junction boxes with still no power. He’s hoping it might be the 4wd ecu behind the glove box and will look into that first thing Monday. Said 2-3 shop hours for that. He said if it’s not that the bill could really start adding up, if I choose for him to start chasing wires through the entire wiring harness

anyone have an advice or been thru similar problems? With two young kids, inflated prices on f’ing everything, money is pretty tight. It’s an 2012 DC with 150k. Love the truck and no desire to get rid of it or get something else that requires a monthly payment. I’m in Colorado and we get enough snow to need the 4wd. At this point I’m only in for the initial $140 diagnose fee, but after that hourly shop rates aren’t cheap on the front range

If you guys have any advice that’s be awesome. And thanks for all the knowledge all you have collected here.

 

I’m sure it’s not the case in your situation, but just before my daughter purchased her “other” Tundra last week, she had mentioned that her Tundra was no longer going into 4x4. She had initially brought it to a local garage and they had diagnosed it being a faulty DS front ABS sensor. They said there was some grease in there, cleaned it up and it seemed to solve the issue. However, a few days later the issue reappeared. This combined with some other issues was enough for her to “dump” the Tundra on dad (I had paid for it and she was making monthly payments back to me).
So, I picked up a “cheap” Chinese sensor and replaced the faulty one, so no issues so far. Also ordered a NTK sensor from RockAuto as a spare.

 

I’ll add that to my list. Thanks for the advice.

 

Did you have and abs light on as well when you had the 4wd issues? I have the same problems but no abs lights and bot front and rear Actuators have been replaced have voltage going to home. But for whatever reason the front one will not engage

 

Are you sure about a rear actuator? My understanding is that Tundras never got a locking rear diff.

 

I meant the one on the transfer case

 

Mine is not throwing any lights or codes. My mechanic also checked the 4wd module behind the glove box. He’s convinced there’s a short somewhere in the main harness. I’ve got an appt at a dealership for a second opinion. If it’s in the main harness I may be f’d. I don’t want a different truck but may go that way.

if your TC actuator isn’t engaging that’s the “first one” in the series. Without that working the add won’t actuate. I’d check your 4wd module and also the switch itself. From what I understand it goes, selector switch, tc actuator, add actuator, entire system engages then you get the solid 4hi light confirming the system is gtg. There’s a really good YouTube video if you haven’t seen it

I’d also check that your 4hi actuator gears have been set to the correct position. After they’re on but the actuator is not installed. Go from 2wd to 4hi back to 2hi. That should ensure the timing is correctly set. Apologies if you already know all that.

 

Do you have the EWD manual?
I’ve come across no power issues on my other Toyota truck and traced it back to corroded or broken wire terminals. Sometimes it is necessary to actually pop the terminal out of the connector to ensure there is a connection which isn’t broken/corroded.

 

Grab the EWD’s from the thread linked in my signature and trace out the circuit for the Multi-Mode 4WD system. You’ll need to unplug and multi-meter test between each junction point to isolate a specific harness. If you find a section that is bad, it may not be that difficult to just replace that section

 

Ok awesome. I will try that. Thank you!!

 

The key to this type of trouble shooting is having a proper probe to penetrate the wire insulation to see if there is power/continuity in that particular wire/circuit. I don’t have one and after watching someone use such a professional tool, I said I need to get one as it speeds up the trouble shooting process immensely and makes it much easier than futzing around with the wrong tools.