My installer is saying that there is a lexus bulletin saying not to unplug the factory amp, because it could cause internal error. Is this true, anyone seen this bulletin?

Anyone unplug their ML Factory amp and when turning it back on, the amp and the HU dont' sync or see each other?

 

If your installer is so sure there is such a TSIB, why doesn't he let you see it? (Hint--there's no such TSIB.)

First he tells you the amp mutes when there's no speaker connected , now he tells you this story.

Time to find a qualified installer.

 

Well he said he can bypass the amp now, he was able to get some tech papers from lexus. He is saying the amp isn't syncing with the HU now that's all. And lexus has given him some procedure on how to do resets, but the HU and the amp isn't syncing now.

 

This car currently is in the shop i manage, and I've been using these boards for Lexus info for a long time, so I thought i may interject here: The TSB is AU001-06. The title is Audio Quick Reference Guide, applicable to all models 2001 - 2007. Its allows access to the diagnosic mode in the radio and states 2 particular codes to look for when scanning it. It sounds like we're trying something that hasn't really been done yet, and i'll keep everyone updated on the process so future installations may go smoothly.

 

Yes, I read that TSIB last night before I posted, and it makes no mention of "don't unplug the factory amp, because it could cause internal error." I also looked at PD009-06 (Power system initialization for pre-delivery service), as well as EL016-06 which discusses initializing Smart Key after battery depletion. I also consulted the Lexus shop manual which describes how to remove and replace the ML amplifier. Other than “disconnect the battery negative terminal” as is their recommendation for every electrical operation, then the usual re-initialization procedure for the windows, etc, there is no mention of special amp re-boot considerations.

Per the TSIB, did you find either error code active? Is the mute line working? Are the TX lines measuring as specified--no paths to ground?

See the 5th picture in this link. This installer disconnected the ML amp to facilitate tapping the signal output leads, and he reported no problem getting his system running again. Might be worth a PM to 16psibrick to see if he can help.

 

At the beginning of the bulletin, its states a caution note. It states upon unplugging the radio wait one minute to reconnect otherwise damage may occur to the cd changer. I was told by a few lexus techs that the note applies to all parts of the system, not the just the changer specifically. The same tech also reported amplifier failures from unbolting them while the car was powered up, which tells me the amplifier is easily damaged by static discharge, which is not the case with any other amp in any other car I have seen. The issue we're facing is upon entering the diagnostic mode at the HU, it does not recognize the amplifier in the system. Both TX lines measure fine.

 

Agreed. When dealing with an electro-mechanical device, like a CD changer (or another example is a PC which uses hard drives), it is always best to let the mechanicals settle and stop fully in case they were spinning. Powering up while spinning can indeed wreak havoc. It is also a good idea to wait for all residual charge to deplete so the everything boots from a known initial condition. The tech is giving good advice. So I guess we all agree it is possible to disconnect and reconnect an ML amp without causing errors or damage.

Disconnecting devices with multiple terminals and power leads, while powered up, may indeed be hazardous to the device, but that does not automatically mean it has problems with static.

So now you’re down to “replace the amp” to see if that’s where the problem lies. Will the Lexus tech give you a loaner to try out?

 

Is your system all up and running now? If so, what was the problem?

 

I'm interested in an answer as well......

 

while installing a subwoofer today with crutchfield on the line, I unplugged the amp to see if there was any power to the plug because the radio had 0 volume showing, When I plugged it back in, my radio went out totally and my windows. I can't find one bad fuse in the entire car.