I have a 2002 Montero XLS with the original Infinity Premium Sound. It does not have the multiple CD changer. Both the front and rear speakers work perfectly with the Infinity - both balance and fader. I bought a new Sony CD/radio head unit with a USB input at Best Buy along with a Metra wiring harness conversion kit. Everything worked properly except the rear left speaker - no sound. I spent hours troubleshooting the problem. I swapped leads with the front and right speakers. I used a continuity tester. No sound from the left rear output. So, I returned the unit and bought a different Sony model. Exact same problem. The rear left didn't work. I ran the same series of tests. No luck. I can't figure this out. The major difference that I see is that the the old Infinity head unit had a different cable for speaker out. But, why do both the fronts and right rear work okay? Any suggestions?

 

Its obviously an issue of the differences in harness connectors. You need to find a detailed pinout diagrams for both unit harnesses and see if you have one or two wires going in the wrong direction (because of differences in design). Whatever you do, DON'T CUT OFF the OEM harness connector if you can. This will make it easier to not have to splice things back to keep checking things with original system.

 

a speaker has two wires going to it. if one is wrong, it will not work.

speakers usually have "paired" wires.
white, white with stripe, purple, purple with stripe, etc.

as Hunter said, find a pinout diagram.

 

Did you use Metra part #70-7003?

 

Good News: Problem solved



I spoke with the installer at Best Buy. He said the Montero with the Infinity premium sound system requires two sets of RCA pre-outs from the head unit for the speakers to work properly. This Sony head unit only has only one set of RCA pre-outs. That’s why the rears never worked properly. I purchased another Sony head unit with 2 sets of RCA pre-outs – now, both front and rear speakers work great. The Best Buy installer expressed surprise that I got any sound at all w/o the RCA jacks hooked up - using the multi-pin connector only. He said the Sony unit with one set of RCA pre-outs would have worked with Y splitters, but the fader control wouldn't have functioned. I used the Metra 70-7004 harness kit. It had all of the right parts - just more than I needed which made it confusing.


The only minor tweak was getting the power antenna to work. There was no corresponding blue wire from the Sony harness to match the blue wire from the Metra harness for the power antenna. So, I connected it to the two blue/white wires for the amp out. IOW, the three wires are twisted together. Now, everything works fine - including the power antenna.


Thanks for your feedback.