Michael7S

The Mark Levinson amp in my 2007 RX400H died after replacing the 12V battery. Well, actually it worked well after replacing the battery on the first startup of the car (and sounded great all the way home). But on subsequent 'key on' it would not deliver sound.

While reading forum posts, diagnosing, confirming power, fuses etc. a funny thing happened. If the battery or the amp is disconnected, the amp will work wonderfully on first 'key on' power. But turn the key off and then on any future power on, you'll not hear from it again. I've proven this over and over while pulling the battery and the amp, ensuring good connections etc.

So after reading every possible post on the Mark Levinson Amp here in Club Lexus, I deduced that it was better to replace it with a 'working one'.

Got a nice clean one, with a guarantee as working, put it in, and guess what? It sounded great! Turn the key off, then back on, and, same as the prior amp. No more sound.

The amp model is 86280-0E010 and both the original and the used replacement are impeccably clean, show no signs of sitting in water etc. The replacement has blue anti-tamper paint on all the important hardware. I opened up the original amp and the soldering is lovely, and coated with some oxidization-proof coating. All caps looked fine. All solder joints looked great. I resoldered some anyway, and cleaned the already spotless connectors and bent them all slightly to ensure extra good connections. Put it in, and it worked great. Until the next power up. This and the new amp do the same thing. If I disconnect either the battery or the amp from the car. It'll work well on the next power up. But not after that.

The RX400H is in immaculate shape, always parked in the garage, no leaks or signs of corrosion. All stock. All systems working well. The head unit is a Jensen CAR710W installed December 2022 and works great. If I turn the Jensen up all the way I can just hear it's output through the speakers.

So, I'm not sure what to do with the car now. My wife commutes now, so no music or Bluetooth is useful without the amp. I can't assume that both amps have the exact same problem. So it's likely it's elsewhere in the car. A speaker suddenly going bad the same day i replace the battery? Unlikely. Seems to be a power issue. I'd love ideas. I'm out of 'em

swfla

iTrader: (1)

You might want to move this to Special Interest Forum as you have a different head unit and you're opening up the old amp. I will tell you that there are more than a few posts where connectors weren't seated properly or a wire got chafed through after an aftermarket install. As this is the LS460 forum, you may also consider posting this in the RX forum as things are bound to be different from LS.

Michael7S

Will do! Thank you. Hmm.. Not seeing an option to 'move' so perhaps post in the proper forum section and delete this one? That's what I'll try if possible.

swfla

iTrader: (1)

One of the moderators can move it for you. Just state which forum you want it in. One of them will likely read that request here and do it. Or just go to bottom of the LS460 main page and scroll to bottom of all threads where you'll find a list of moderators who you can contact. Good luck.

Michael7S

And fixed. TLDR: The 2007 RX400H (and probably many other Lexus models of this era) BCM needs to see the OEM stereo at least once after a hard reset to allow an aftermarket head to turn on the power amp.

Details: The Axxess tech support folks were correct. Here's what we think happened:

1. When the 12v battery was changed, the Lexus BCM (Body Control Module) experienced a reset. This caused it to reboot, which in turn tells it to 'hunt' for some proprietary signal that only the OEM stereo sends.
2. My aftermarket Jensen head unit does have an Axxess conversion box that takes care of 'everyday' Lexus/Toyota specific signals to turn on the power amp, but it does not feature the signal that 'pretends' to be the OEM stereo when the BCM recovers from a hard reset.
3. So since the BCM could not find an OEM stereo, it refused to send a signal to the Mark Levinson power amp (both my original and the replacement amd)
4. I had disposed of the original factory stereo (after trying to give it away for months). So I bought another one on Ebay for $380, plugged it in and turned on the key. All worked perfectly. The rebooted BCM was convinced there was an OEM stereo installed.
5. With the key on, I turned the OEM stereo off (volume ****) and swapped the two larger plugs back to my Jensen/Axess system. All now work perfectly.

So I'll keep the OEM head unit around in case this happens again. I'll list my original working amp on Ebay so someone else can benefit if they lose their amp.

Two takeaways: Crutchfield support is awesome. They sent me an $86 Axxess box next-day-air without question - simply to help me diagnose what the problem was.
And Axxess tech support is very knowledgeable. About 30 seconds to convey the most likely problem.

Hope this helps others.

LeX2K

Thanks for the update you jumped through enough hoops to join the circus.

swfla

iTrader: (1)

Lexus doesn't play well with aftermarket, no matter the system.

ecsclean

Many thanks for your great post and information!

I too have worked out that it seems to be the only way to get the amp started. I have the old headset and just have to connect it every time I remove the battery etc. A bit of a pain!

Paul.