I just had the actuator motor replaced on my 2008 4Runner. The system will function correctly now and will go into 4wd but the lights on the dash continue to flash like it’s not working. The light will turn solid when I push the differential bypass button. When I turn the differential back off, the rear light will flash. No problems with going into 4lo. It seems something is not calibrated or set right. The mechanic doesn’t know what to do. Any help or suggestions is greatly appreciated.

2008 4Runner Sport w 4.0L V6.

Thanks!

This is very likely not the issue since you seem to know what you're talking about, but just to cover all our bases: When switching modes, the engine is running with the gearshift in NEUTRAL, correct?

I second this comment that I don't think this is the case as you seem to know what you're talking about BUT..... Did you switch to "D" and go slowly down the block to see if the blinking stop?

It's possible that the timing on the actuator is slightly of. Strange though that you are only having issue in 4Hi. To go from 2Hi to 4Lo you have to engage both 4WD (same as 4Hi) and 4Lo (there are two rods on the actuator). As @blackjackck said, first try engaging 4Hi and drive for a bit to see if blinking stops. It's normal for it to blink for a while when you first engage it and driving rotates the gears and lets it to engage.

Thank you for the feedback. I have driven for several miles and the flashing is consistent. I’m wondering if a sensor is going bad or timing maybe? There was some discussion about resetting the ESU unit after replacing the actuator but I don’t know how to do that.

There is a timing switch inside the actuator that tells the 4WD ECU what position the actuator is in. If that switch is off the ECU does not know that 4WD has been engaged. The switch position can be seen from the outside, all you have to do is remove a small metal cover. When in 4Hi the blue mark lines up with the black mark. If it does not you have a timing issue. More details in this thread:

Water in actuator, now stuck in 4lo, and how to fix it

I am still confused why 4Lo would work but 4Hi not. Another thing to consider is that there is a second actuator on the front diff that needs to engage when you switch to 4WD. If that one does not engage (or was in the wrong position when the new actuator was installed) you might also get a flashing light as the ECU gets confused. If you had a mechanic install it I would have him deal with this before you mess with the new actuator.

One to add. After locking in the differential and when O unlock the differential, the green 4wd light will stay on but the yellow 4wd light will start blinking again.

I know this is an old thread but were you able to find the issue? I have the exact same issue. I replaced the front transfer case actuator because it was shot. Everything works fine but the light is still flashing.