4wd dash light doesn't work

Truck: 2003 Tacoma TRD 4x4 Double Cab V6 automatic with "One Touch 2-4 Selector" on transfer case lever

The 4WD light will not illuminate on my "Combination Meter" (FSM name).

I am pretty sure my 4WD system is working. I hear the relay click and the ADD engage when I engage the "One Touch 2–4 Selector" button on the transfer case lever (I don't have the J-Stick).

I took apart my dash and swapped bulbs between the ECT and 4WD and confirmed that the bulb is fine.

Tomorrow morning, I'll dig into the "A.D.D. CONTROL SYSTEM (4WD)" page SA-67 of the 2003 FSM. This will confirm whether or not the signal going to the ECU and dash is trying to tell the bulb to turn on or off (I'm guessing this is the issue).

Any other ideas while I sleep?

 

I think youre right to go after the A.D.D. Maybe its a bad connection. Not sure if you have a vacuum or electric operated A.D.D. but you may check the connection.



Unplugging this cable would duplicate your symptom. I have the vacuum A.D.D. and the blue connector sends a signal for the A.D.D. to engage while the brown one sends a signal for it to disengage. (I unplug the blue connector periodically to enable 2 Lo when I need to back a trailer).

Anywho, try checking connections. Also try looking under your truck to see if your front driveshaft is spinning when you have the selector in 4WD. It will at least confirm if it is/isnt working. Good Luck!

 

Thanks for the feedback. As I was reading "see if your front driveshaft is spinning" I realized I could rig up the GoPro to let me know since I don't have anyone else to check for me.

 

Update: I put most of the dash back together last night before turning in.

This morning I decided to start with something a bit easier - extending the RS3200 range and the "free security system" upgrade. When I was changing a setting with the unlock feature, I noticed that the light went on when the ignition was on.

I disengaged the "One Touch 2–4 Selector" button and the light went out and I heard the ADD disengage. When I pressed it again, I heard the ADD working but the light didn't go back on. Since I have the kickpanel plastic off, I tapped the 4WD ECU and the light went back on.

Seems like I have a loose connection at or near the 4WD ECU.