2004 Prius - Low volume on right front/rear speakers

Hello,

I've had my 04 Prius Package 9 for a while, and have intended to keep it probably until I run it to the ground... Anyway... over the past couple of months, I've noticed that the right front speaker tended to go out and come back every so often, sometimes associated with turns, but not consistently.

Today when I finally sat in the car to see if I could diagnose the issue, I made the sound come out exclusively out of the right speakers (using the MFD AUDIO button with the speakers fading to the right and center) and I still hear both, but very faintly. Even at 40+ volume it's still faint. Both right front and right rear exhibit the same faint sound volume/loudness.

However, left front and back speakers are fine and plenty loud. Is this an amp issue, or is there a chance there's a bad connection somewhere? I tried to disconnect/reconnect both cables leading to the JBL amp under the passenger seat, but that did not fix it.

 

I don't see a good way of doing that at the amp side. Do you mean at the speaker connector side? I had saved the repair and electrical manual waaaay back when I bought the car, so I have those and I'm looking into it. One of the diagnostics involve getting to a harness on the back of the radio though, and doing a Sirius install myself years ago, I remember it was a pain the rear end to do that...

I took apart the JBL amp, didn't see any leaking caps or anything that looked bad -- the board seemed pretty much new. I put it back together and connected it back and the problem remains. I don't get any DTCs on the LAN error MFD screen relating to the amp (besides the obvious time I disconnected it)

My next step is looking at the speaker connectors under the passenger dash kick panel...

 

Well, the connections under the passenger dash kick panel were not the problem, but the one under the driver side kick panel were -- which is odd, since that one just controlled the front/rear left speakers. I unplugged and replugged the connectors and all of a sudden the right front/rear speakers started to work again. I jiggled the connectors and didn't see any obvious issue of them going out again.

Notice I said connectors.... I did the driver side kick panel blind without looking at the manual, and disconnected IF1 by mistake while I was in IG-ON (ACC ON mode beeps from driver side door being open prompted that stupidity) -- that one was "Floor Wire and Engine Room Main Wire (Left Kick Panel)" Oops! That one triggered a check engine light and red triangle that persisted through about four off/on cycles. When I looked through later in wiring diagram IF1 has cables to the HV Battery ECU as well as the fuel pump, d'oh!

In case this happens to someone else, the symptoms I had was that both the top and bottom speakers on the left front and rear had the same low volume effect, I just had noticed the right front going in and out a few months ago because it was the closest to me (vs the back right rear). The fix was to re-seat the front/rear left speaker connectors on the driver's side kick panel -- ID4, and IE2, as per the electrical wiring manual.

 

It could certainly be possible it was a bit of corrosion, you're right. I didn't do much except blow on them and shake them a bit, so perhaps that was enough. I didn't look at the pins themselves to see if they needed any cleaning, bit of an oversight there, haha.

Thankfully the driver's side speakers were fine, it's possible that my left ear is not as sensitive 'cause it took me long to attempt a fix.

 

So the issue reappeared over the last few days, and I noticed that the issue was only happening when I was listening to the factory Sirius tuner I had installed years ago. The first tuner I got (PTS31-00052) failed under a year of use and I had it replaced under warranty with the one I have now. Tthe original one I had was discontinued, and the new part number for the one I have installed now is PTS31-53060, IIRC.

I have the tuner mounted behind the rear seat on the driver's side -- I disconnected the wiring harness and reconnected it, and sure enough the right speakers started working fine again when using the SAT radio mode. I didn't see corrosion on the connector, but again I did the usual blowing air and re-seating it. At this point, it might be either the harness or the tuner itself.

I forget exactly how the original tuner failed, but I think it might have been a no audio condition for all speakers, regardless of volume, but all at the same time, so it's hard to tell right at the moment if this is harness or tuner module related, but it definitely removes every other component besides those 2 from the failure chain. If it ever completely fails I will deal with replacing it, as I actually paid for a $77 Sirius subscription this year.