[Mk2] [NA] Annoying radio buzz / whinning noise (updated FIXED!)

[GMLMR2]

Annoying radio buzz

Hi folks been a while since I been here, anyway a problem I have that is quite frankly getting on my goat, couple months back I started up the car and I could hear what sounded like a fuel pump noise, I put my ear to the footwell next to the pump and it sounded fine, I accidentally switched the radio off while I was listening in the footwell and the noise went away :S turned it back on and the noise came back so I thought haa a radio fault, so swapped the unit out for another kenwood cd player all fitted up, started the car and the unit worked no noise problem solved,

well I went to fit a new kenwood mp3 unit last night and hooked it all up correctly and all works, I later took the car out and as soon as I started the engine the noise I had previous was back this time with vengeance, I quickly put my old unit back in and it made no difference, no matter what unit is in now, the noise is continuous, no amount of wiggling leads etc makes it go away.

I did find a guy on youtube with the same problem the noise you can here in this video is exactly the same as I’m getting, is this common problem among aftermarket units.

http://www.youtube.com/watch?v=rIA_-ZjER-E

The MR2 is 1993 Import Rev2 with the Active Sound System, my Kenwood hooks up via iso connector that also has RCA plugs for which I plug straight into the back of the head unit, after 4 years of ownership I’ve never had a problem until recent, I don’t really want to swap out the stock amp and speakers as the stock sound is fine it all worked fine before so why should it be any different all of a sudden

I hate anything to do with wiring but one thing I did notice when I first bought the car and fitted my first radio was why I didn’t work when I first initially hooked it up, I’ve had all fords and with them you just plugged the block connector in the back and lights on radio working but with my mr2 no head unit will power up unless the Arial is plugged in, I never listen to the radio so I’ve never hooked up the aerial leads in previous cars, so is this radio ground because I thought using an aerial for ground would be a bad idea,.

[GMLMR2]

Problem solved turned out to be iso wiring loom, I made some alterations to the loom, the reason why it came back was due to the Kenwood inline power suppressor had gone, but I thought there must be a way round this because suppressors only mask an existing problem so I downloaded a complete set of wiring diagrams for the radio layout for the stock radio and the active system and basically made some alterations to the ISO loom so the active systems thinks it’s running a stock unit haaa!!

I’ve found out that grounding is essential with the active system, but a ground any old where wont work…so read on.., It is important that if you intend to use the MR2’s active system then all 4 pre amp RCA’s must be connected to the head unit and grounded via the iso loom, if your Head Unit only has 1 preout then buy 2 Y splitters to connect the 4 RCA’s to the preouts, failing to hook up the rear ones say will give you this dreaded noise as I just found out earlier, also the preouts “MUST” be grounded via pin 11 of the ISO loom, my RCA’s were not grounded by pin 11 and this is the reason why the noise I was getting was running through the speakers, I made this alteration to my iso loom and problem sorted I have no suppressor’s anywhere now and there isn’t even a hum, pop, click or whine coming from any of the speakers only top quality “The Shamen” music, I’m glad as I’ve always been impressed by this cars speaker system and that layout of the stock system lol I really didn’t wana rip it out due to some dodgy noise.

Oh and by the way this mod works on MR2’s up to 93 which is REV 1 and 2 with the 14 pin iso connector, the ISO connectors were changed on the later models to a 15 pin in which case all you need to do is pull the black ground from 10 and slip it into pin 12 on the iso loom and from what I’ve read on the net it cures the problem on later MR2’s

I made a little diagram of pinout to help anyone with this irritating problem.