Today while driving the stereo simply cut/lost its sound. Radio and everything else still works buttons screen, just no sound. Turned the car off, it sat for 5 mins and turned the car back on. Sound came back for nearly 20 sec and then cut off.

Looking over the Lexus history the ML amp was replaced with what Lexus history shows as an upgraded amp per TSB about 30-40k miles ago if I recall.

The previous amp issues when it failed was the chipping noise, correct? Could I still potentially have a failed amp? Any other thoughts before I take this to the dealer?

Thank you.

 

It certainly sounds like the amp. Absolutely take it back and have them look it over.

 

small update:

I've discovered the stereo cuts out after about 45 mins of driving - i.e. continuous playing of the stereo for 45 mins. My initial post was made shortly after my first drive today. Then on my way home, same drive and 45 mins later the stereo cut out again..this time more slowly. It sounded as if radio reception was going bad...the speakers started to crackle and fade until there was no more sound. I pulled up the one interior trim panel covering the ML amp in the trunk and while the amp wasn't extremely hot, the metal floor/body of the car the amp is bolted to was extremely hot. Not sure if this has any affect on the amp and its performance.

I haven't seen a post yet where someone has mentioned the stereo cutting out without a chirping noise, like mine is currently doing. All previous posts describe the chirping symptom once the music dies. Mine is not doing that...there is simply no music after about 45 mins.

I might also try calling United Radio to see what they say.

 

I'm not an expert on the ML amp, but in general most amps do have a thermal cut out. So amps have fans and some dissipate heat through fins, but all by design will get hot and need cooling. I would leave the amp uncovered and open to as much air as possible and see if heat is your problem. Maybe even unbolt it and move away from your hot spot.

 

It's out of warranty. Lexus will charge a fortune. A United radio phone call makes the most sense. I know you're looking for a quick fix but, you're not gonna fix this without sending it in. Sorry.

 

I got a return call from United Radio after sending my amp in to them. The amp tests perfectly fine. I'm at a lost at what else it could be at this point.

UR is sending me a pin out of the amp to test a few things with a volt meter. I guess I'll try that but otherwise I may just take it to the dealer. Could my head unit be going bad?

 

You're in an unenviable position. I think that a lot of repair shops do a parts change rather than an in depth diagnosis. You did the right thing by sending the amp in. Now it seems that the head unit needs to be tested. Not sure if the dealer will actually test it or just put in a new unit and charge big money. I'd send it to United Radio to let them test it after performing the tests they recommended to you (worth doing). They are the most affordable route. If it's unrepairable, there's always eBay and salvage. A new one will be very expensive. Then there's always aftermarket as an alternative. No quick affordable fix here. Keep us posted.

 

I was thinking the same...send my head unit into UR. I have a friend that works at Lexus who said there is a dealer only code screen. He can help me access it to see if there are any codes on it relating to the radio system. He did also mention that if I were to take it to the dealer and they found the head unit defective they would likely replace it with a refurbished unit. BTW the looked up the head unit and its nearly the same cost as the amp new.

My other thoughts are to buy a used amp and see how it performs...if I get the same symptoms then I also know my original amp is good.