97 LS w/nakamichi - no sound - how do I troubleshoot amp? - ClubLexus - Lexus Forum Discussion


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97 LS w/nakamichi - no sound - how do I troubleshoot amp?

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Old 12-23-13, 05:22 PM   #1
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Default 97 LS w/nakamichi - no sound - how do I troubleshoot amp?

Today as I left on a 1600 mile trip out of state, my stock stereo failed me.

I can hear the faint sounds of my music when the volume is turned up to the max.

The head unit behaves as it always had, just no volume. Not from cd or tuner.

My first thought is the amp failed, but I don't want to buy a replacement oem amp unless I'm more certain...

Any thoughts?
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Old 12-24-13, 06:48 AM   #2
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Test your amp in another similar 95-97 LS400 with Nakamichi - quick and easy to do. If your LS has a Lexus phone system, its ECU in the trunk could be shorted out and putting the audio system in mute mode as if a phone call is in progress - a very common problem. Bypass the phone ECU if it has one.

Edit: Now that I'm typing on a PC instead of a phone, I'll provide more information.

It is easy to remove an amp - Pioneer or Nakamichi - from a 95-00 LS400. Just put the front passenger seat all the way forward and tilt the rear of the seat cushion up as high as possible. Lay your amp on the back floor of a similar LS400 to test it. It's not necessary to remove the amp from the car you are testing your amp in.

Based on what I've read on forums over the years, the failure rate of 95-00 Nakamichi head units is much higher than the failure rate of Nakamichi amps. I had a similar low volume condition in my 00 LS400 with Nakamichi. The first time in 2008 a repair shop resoldered the volume control to fix it. When it happened again a few months ago, I had the Nakamichi head unit replaced with a really cool Kenwoood DDX470 double-DIN using the Nakamichi amp and all the original speakers including the subwoofer -- it all works great. There is a post in the LS400 audio thead about it.

As I said, a defective phone ECU can also cause low volume. If your LS has a phone ECU under the false floor on the right side of the trunk, unplug all the cables from it and plug the large male and female connectors together. Tuck the cables up out of the way so they don't get wet. On cars without phone systems, the phone system cables are normally connected to the bottom of the tool kit receptacle. A friend had a low volume problem in his 99 LS400 with Nakamichi. The audio system sprang to life instantly when we bypassed his phone ECU.

Last edited by Kansas; 12-24-13 at 07:07 AM.
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Old 12-24-13, 10:53 AM   #3
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My 2000 LS400 with Nakamichi has a similar problem, only in my case passenger side speakers will stop working intermittently and the drivers side speakers will continue working as normal. Similar to your problem, there is faint sound coming from the passenger side speakers if I turn up the volume all the way. This usually happens on longer trips after the head unit is completely warmed up. I can temporarily fix the problem by turning the head unit off and on. Sometimes it takes a few tries and it usually only lasts a few minutes until the passenger side speakers quit working again. Very annoying.
I originally also thought it was the amp so replaced it with a used unit from ebay, however this didn't fix the issue. I'm quite confident the head unit is faulty in my case. The car didn't come with a phone but I'll check it for a phone ECU regardless as per Kansas' recommendation.
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Old 12-24-13, 11:08 AM   #4
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Well, I bypassed the phone, but it didn't help. Too bad, I really thought that made sense. I don't have another LS I can swap the amp or hu in to test, so not really sure what my next move is. Unfortunately there aren't very many ls400s where I live, and I don't know anyone with one. The local used car lots aren't going to let me start messing around with their cars....

Frustrating, this road trip is really sucking..
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Old 12-24-13, 11:55 AM   #5
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Quote:
Originally Posted by dma251 View Post
Frustrating, this road trip is really sucking..
Bummer. What part of Washington? Is there a repair shop nearby that specializes in Lexus? They may know of a 95-97 LS with Nakamichi you can test your amp in. I was lucky to have that friend with the 99 LS with Nakamichi but that car is long gone and crashed. It really is super easy to test your amp in another 95-97 LS as long as it has a working Nakamichi system. All you have to do is remove the connectors from the amp in the "donor car", lay your amp on the rear floor and plug the cables into your amp.

Edit: When you bypassed the phone ECU and plugged the large male and female connectors together, were there any signs of corrosion on the pins/etc. inside the connectors? Any broken wires? I just remembered a case - on this forum, I think - of where wires leading to these two connectors were so corroded that they were falling apart. If I remember correctly, the last I heard was that the person was going to chop off the connectors and solder the wires together - except the wires were in such bad shape that he could not tell which wires to connect.

Last edited by Kansas; 12-24-13 at 12:04 PM.
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Old 12-24-13, 12:13 PM   #6
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Default One more idea ...

If your Lexus phone handset is still installed in the upper console tray, make sure that it is not plugged into the connector on the driver side underneath the vent you see when the armrest is raised. That connector also has a mute pin - I think the connector on a 95-97 I am referring to has three pins. Actually ... unplug your phone from any connectors under the rear of the console. There may be three separate connectors. How the connectors are used may depend on which Lexus phone you have - the portable or the fixed.
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Old 12-24-13, 04:56 PM   #7
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Well, I believe you are correct it is in the head unit. But life just got a whole lot better -

I am in Washington state traveling to Missoula Montana for a few days to get away from my extended family. My wife and I got the chance to talk to each other for the last few hundred miles, which was nice.

I've been irritated most of the way by not having anything to listen to besides ourselves. I have loved and preserved this car for years into the point most people would have sold-off a 16year old luxury car, but it's a perfectly stock coach edition, and It's taken very good care of me - until now!

At a small gas station I lazily gave the volume dial a halfhearted twist just out of habit and heard the crackle and sizzle of a volume **** giving out... Tried it again with it hooked to my iPhone and I had sound as I used to!

My assumption now is I have a failing volume control, which is just the push I needed to finally ditch this cobbled together iPhone input cable tapping into the cd changer with a charge lead off cigarette lighter setup I have. It's gotten really bad buzzing and interference from my phone rf.

How tough will it be to integrate a new Bluetooth-capable double-din head-unit into the otherwise stock nakamichi amp/speakers? Aren't the stock speakers 8ohm, meaning I would need to keep the stock amp, or replace all the speakers too? I don't want to replace a sound system i am overall pleased with the sound quality.

Thanks a lot for your help, though. Cross your fingers it holds out for the rest of my holiday road trip.

Last edited by dma251; 12-24-13 at 05:01 PM.
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Old 12-25-13, 01:27 PM   #8
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Quote:
Originally Posted by dma251 View Post
How tough will it be to integrate a new Bluetooth-capable double-din head-unit into the otherwise stock nakamichi amp/speakers? Aren't the stock speakers 8ohm, meaning I would need to keep the stock amp, or replace all the speakers too? I don't want to replace a sound system i am overall pleased with the sound quality.
There are lots of other posts in the LS400 audio thread on installing a double-din - here is mine: https://www.clublexus.com/forums/8219167-post329.html

It doesn't matter what ohm rating the OEM speakers are as long as an OEM amp is used to drive them. The Geek Squad / Best Buy installer used specialized hardware to connect the wires from the Kenwood to the OEM audio system harness in my 2000 LS400.

No wires on the OEM audio system harness were cut. No connectors on the OEM audio harness were chopped off. No soldering was done. The install is easily reversible. The deal with Best Buy includes reinstalling my Nakamichi head unit at no extra cost if I ever want to but I could easily do it myself in less than 30 minutes.

I've since tuned the Kenwood's equalizer better to my liking but I think the Nakamichi head unit had a warmer sound. The Kenwood's sound is "cleaner" than the Nakamichi head unit's - less "muddy" or "warm" (whichever way you want to call it) - and more like that of the standard 98-00 Pioneer head unit.

I particularly value the Kenwood's Bluetooth audio streaming feature. I normally put my phone in its charging cradle but it is nice to be able leave it in my pocket and still stream audio from it if I am making a lot of stops on the way home from work. If get out of my car while streaming from Pandora or from the flash memory on the connector on the USB cable I routed to the upper console tray, the Kenwood is smart enough to start the audio where it left off when I restart the car.

I might have installed a cheaper, lower feature aftermarket head unit if I wasn't likely to pass this car to a friend or relative next year.
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Old 05-12-14, 03:45 PM   #9
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Quote:
Originally Posted by Kansas View Post
Test your amp in another similar 95-97 LS400 with Nakamichi - quick and easy to do. If your LS has a Lexus phone system, its ECU in the trunk could be shorted out and putting the audio system in mute mode as if a phone call is in progress - a very common problem. Bypass the phone ECU if it has one.

Edit: Now that I'm typing on a PC instead of a phone, I'll provide more information.

It is easy to remove an amp - Pioneer or Nakamichi - from a 95-00 LS400. Just put the front passenger seat all the way forward and tilt the rear of the seat cushion up as high as possible. Lay your amp on the back floor of a similar LS400 to test it. It's not necessary to remove the amp from the car you are testing your amp in.

Based on what I've read on forums over the years, the failure rate of 95-00 Nakamichi head units is much higher than the failure rate of Nakamichi amps. I had a similar low volume condition in my 00 LS400 with Nakamichi. The first time in 2008 a repair shop resoldered the volume control to fix it. When it happened again a few months ago, I had the Nakamichi head unit replaced with a really cool Kenwoood DDX470 double-DIN using the Nakamichi amp and all the original speakers including the subwoofer -- it all works great. There is a post in the LS400 audio thead about it.

As I said, a defective phone ECU can also cause low volume. If your LS has a phone ECU under the false floor on the right side of the trunk, unplug all the cables from it and plug the large male and female connectors together. Tuck the cables up out of the way so they don't get wet. On cars without phone systems, the phone system cables are normally connected to the bottom of the tool kit receptacle. A friend had a low volume problem in his 99 LS400 with Nakamichi. The audio system sprang to life instantly when we bypassed his phone ECU.
Thanks Kansas! that solved my no volume radio problem.........awesome!!!! It was the phone ECU in the trunk on the right hand side I wondered what that was for. I unplugged all the connections and then plugged the male and female together......stereo cranks loud now!

Last edited by BluesImage; 05-12-14 at 03:48 PM. Reason: added about the phone.
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Old 05-15-14, 02:17 PM   #10
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Thanks guys. 1999 LS400 Nakamichi stereo without phone set up. I followed the procedures suggested and they worked!! I once again have sound but for how long, who knows? I guess it was the dirty ECU connection in the trunk below the tool box because when I took the plugs apart, blew out the dust and replugged the male and female connector, it worked. That solved my no-volume radio problem.
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Old 05-16-14, 06:16 AM   #11
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Ima have to check this out...i cant find my antenna anywhere
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