Hey felllow 4th gens! Reaching out for help. My google fu is apparently weak. I found some results focusing on zero point calibration, but my my yaw sensor looks good when reading the ecu. Closest thing I found was in the ih8mud forum for a gx470 with a similar problem and iffy solution. My C1340 vsc trac off lights fix | IH8MUD Forum

Last week I switched into h4 and noticed my vsc off flashing and trac lights on. The lights stay on when I switch back to h2 and only go away after I restart. They come back on as soon as I switch to h4. I get one error code of c1340. Anyone experience something similar?

Fingers crossed.

c1340 has to do with the center differential circuit. You have a possible bad switch, open/short in the harness or a malfunction with your 4wd ecu. Calibrating will not fix this issue

Thanks cjimen! Taking my truck in Ml onday and this will be helpful.

Just thought I'd share in case anyone else deals with this. My local mechanic went through the diagnostics for an open diff lock circuit error, c1340. Wiring seems to be good, but struggles to get into 4l; didn't work when mechanic tried. Let me know that it was likely the 4wd actuator or 4wd ecu and that I would need to take it to a transmission shop or the dealer. Want it done right, so I chose a nearby yota dealer with a good rep. That was yesterday morning. They called me yesterday evening and and still running through the diagnostics. Let me know that the wiring looked good. Asked me questions about how often I used 4l and if it happened on the trail or road. I use 4l about 3 or 4 times a year. I don't cycle my 4h and 4l monthly as I should. I have about 180k smiles on her. Dealer seemed unsure what was wrong saying that c1340 could mean other probs like abs. I have a feeling this could be expensive...

Expensive af! Tech at the dealer let me know that the problem is an internal fault of the hydroboost unit and it needs to be replaced - $3500. Doing it.

Maybe this:

4th Gen 4Runner Master Cylinder/ Brake Accumulator Replacement - YotaTech Forums

Probabaly not...

Just wanted to update the community on this issue. Toyota techs weren't able to figure it out. They replaced the hydroboost assembly and the 4wd transfer case actuator to no avail. Didn't charge me because I still get the same lights. Hi and Lo 4wd still seem to work as does my center diff lock. Tried a few other things like replacing my gas cap (was loose fitting) and brake switch with no change. Still bugs me the lights come on as I described before, but with 4wd and the center locking as it should, I'm just driving it and taking it on trails with no problems. The mystery remains.