Long time listener, first time caller. I have a 14' GS with the standard pioneer sound system. Since I got the car and they performed several car washes, I've had periods where the sound would cut out then come back, my guess was moisture getting to the amp. As of late it is getting worse and has completely cut out for a month+. I have swapped out amplifiers 3 separate times, checked the radio fuses, verified I have 12 volts at the amplifier harness, verified I have 12 volts on the white cable on the MOST connector at the amplifier, tried a different stereo, and visually checked the MOST connection under the shifter. I am stumped. I also had something strange happen in the diagnostic interface. The attached picture was when I first started diagnosing the issue, and shows "1 : AMP NCON". After taking the stereo apart and checking different connections, that line has completely disappeared and I am left with the EMV-M, DISP, and R-TOUCH.




Anyone understand what may cause the 1: AMP line to vanish? When I look under EMV-M, it states AMP OK. I'm about to give up and bring it to a shop but I was hoping someone with more experience with this system may be able to give me some better direction. Thank you in advance for the help.

 

Where did you get the replacement amps from?

 

All from eBay but different vendors with good ratings. Wasn't 100% sure they were good but after trying three separate times I figured I would of had one good one.

 

Did it continue to have the same exact - EMV-M, DISP, and R-TOUCH message displayed each time with every replacement Amp? Nothing changes at all?

 

I only found out about the diagnostic screen as of late. But I can say that the screen is exactly the same with the original amp and the most recent eBay amp.

 

This is how the screen looks currently.

 

From the past, 9 times out of 10 it is always your Amp. This may be a Software load problem, but I don't really know? Did this happen during a battery disc? Did you try the Reboot of the system?

Maybe he can help, he's excellent at these kind of things. @EAST

 

Negative on the battery disconnect. I will try a system reboot and report back. Appreciate the help so far.

 

I think this is that system:

1. Remove the battery terminals for positive and negative
2. Leave the battery unplugged for 30 minutes to an hour (may actually require less time but this is how long we waited)
3. Press the Start button once to turn on the accessory/battery mode (DO NOT HAVE YOUR FOOT ON THE BRAKE AND START THE CAR). *If you start the car the screen will still remain black and you will have to start over
4. Press the PWR/VOL button to turn on the Radio
5. The display screen will light up and show a progress bar showing it is loading the information from the SIM card. Once this completes the system will reboot and the display will light up as normal.

So you are saying you disc the Neg battery term, then when to put back and started this is when this problem started?

 

Haha I see how that was confusing. Sorry I was saying I did not touch the battery while this issue was happening.

 

Performed the system reboot. Unfortunately still no sound and diagnostic screen is showing similar information as before. Only difference is DISP says OK.

For what it's worth, my gut is telling me it's a connection/wire issue. My only problem is all the tests I did with my volt meter say I'm getting power and have ground. Might of mention this before but I don't have an Oscilloscope to verify the MOST signal is getting from the radio to the amp.

 

Can you get to the home Map screen, and just no sound? What exactly happens when you cut the car on? What does it show on your screen?

 

When you say you "took the stereo apart", do you mean you took out the head-unit or the amp? If the head unit, I wonder if one connection may not have clicked back in properly for you to not have an AMP line anymore.

I doubt it will do much, but have you tried selecting the "Recheck" or "Memory CLR" options? It seems for Memory CLR, you have to select it for 3 seconds. At the very least, I'd say select the Recheck every time you do a change, just to make sure whatever action you did shows the latest status.

 

@ JGSCOTT It is unresponsive with the volume/power ****, the steering wheel voice command button, and the steering wheel volume control. The balance and fader settings are also greyed out. Other than that the infotainment system operates as normal with my navigation showing up and the radio provides information relative to the station.

This is similar to what I have seen in this forum and youtube videos on other Lexus models. Like you said 9/10 times its the amp. However I am thinking it may also be a connection issue between the amp and head unit, basically acting like there is no/bad amplifier. I saw one Youtube video where the same issue on an ES was caused by a faulty ground. My other last ditch effort I am trying is to find another 2012-2015 GS in the area and bribe them to let me plug in the two amplifiers I have on hand. May help eliminate one variable.

Hi East. I removed the amp more times than I can count, but I have recently also removed the head unit from the center console. I can open it back up and check the MOST cable connection and the Amplifier harness to see if they're loose.

I did try the recheck and memory clear option, but no luck. I appreciate the help, anything you can think of keep throwing it out there and I'm happy to try. The only good news is the GS is a quiet ride so its not like I have to listen to a bunch of rattles or squeaks on my ride to work.

 

UPDATE: Bribed the CNC operator to let me play in his ES350. My original amp was dead. The new amp from Ebay is working properly. As of now neither work in my car. I will take the head unit apart and confirm the connections and hopefully that resolves the issue. I will report back here with updates. Thanks for the support so far.