I need an electrical Sherlock Holmes (1 Viewer)

[starclassic]

So I have a professionally installed aftermarket head unit (Kenwood DDX6704S) in my '99 (non-nav) LC. I'm driving the other day and it just turns off. Goes totally black, no power at all.

I get it home, check all the related fuses — nothing. All fuses are fine, including the one in the back of the head unit.
I realize the radio antenna has no power either — I realize this might be an unrelated issue. But I did confirm that with the ignition on, the antenna motor doesn't even spin. It's totally quiet.
I disconnect the Kenwood h/u and reconnect the stock radio to the stock connector. No power. So now I'm thinking it's something wrong with the amplifier?
I remove the passenger's seat and get in to take a look at the amp. Everything seems fine, nothing loose or corroded. So I grab my multimeter and my FSM, and proceed to test the A and B connectors at the amplifier. And I get these results (see penciled notes at bottom right):

Now, I am not an electrical pro by any stretch. But I do know how to use a multimeter. Based on the notes penciled in above, it would seem that I have an issue with the A connector/wiring harness. But I don't really know what to do next.

• All the tester connections check out except the A3 constant and A9 ACC/ON.
• A3-ground constant is supposed to reflect battery positive voltage but only registers .5-.6V
• A9 -ground with ignition ACC or ON is supposed to reflect battery positive voltage but registered a slight negative voltage of -.5V

Does all this mean my factory A wiring harness is bad? I really have no idea what to do next. Replace the amp?

Would appreciate some help. It sucks driving around with no functioning head unit!

Here's a shot of the back of my head unit for additional info (kind of a tangle but all the connections seem very secure)...

 

[jerryb]

something silly maybe. But I'd check the kenwood to be sure it boots with 12v.
Other than that, id toss the amp and buy a 4 chan class D and call it a day. Way faster, and in the end you may find out that the stock thing is toast.

 

[starclassic]

something silly maybe. But I'd check the kenwood to be sure it boots with 12v.

Okay! Maybe this is a dumb question but how would I go about booting the Kenwood?

 

[ramangain]

Do you get continuity between pins A3 and A9? Give the connector a few tugs and yanks while testing for continuity.

If you rig up a temp +12V line right from you battery to your +12V and ACC leads of the radio, will the radio turn on? (Ensure the ground wire is grounded too) Just confirm the headunit is OK, essentially. If it does, do you get sound out of the speakers when a source is selected?

 

[ogsuv]

I agree with some kind of temporary wiring to make sure the Kenwood lights up (my guess is the kenwood is not the issue)

bypassing the factory amp is a good option, although you lose your subwoofer.

Metra 70-8116 Amp Bypass Harness

Allows you to install a new car stereo and bypass the factory amp in select 2000-06 Toyota vehicles

www.crutchfield.com

You probably still have some testing to do to determine exact cause, but if you are getting .5v at the input side at the amp, seems like it would be a corroded wire at the fuseblock, or some other weirdness....

I bypassed my amp basically the day I brought it home 5 years ago.

 

[Skidoo]

The negative voltage is weird and weird things a lot of times are caused by bad ground connections.