2007 Trailblazer LS - OEM (UBO) Radio - Very little sound

[ZTatZAU]

Hello, I'm new to this forum and this is my first post here. I am not a car audio guy but I do need some car audio help!

Recently picked up a very nice, 1 owner, low mileage 2007 Trailblazer but the OEM GM radio had no sound. If the volume was turned all the way up, you could hear very faint, tinny sounding, mostly treble, AM/FM/CD sound from the front door speakers. L-R BAL control seemed to work normally and FADE F-R seemed to work too but produced no sound at all from rear. My research indicates this is an original RPO code UB0 base level GM radio, no Bose, no Premium, no separate amplifier, no steering wheel controls, and perhaps even no rear speakers. I haven't yet pulled any door panels but the radio wiring behind the dash seems to be all unmodified GM stock.

To this novice, the OEM radio's output sounded like an unamplified pre-amp signal but with no external amplifier, I figured whatever the failure was, it had to be in the OEM radio. So I purchased and installed a JVC KW-V660BT head unit with the various Metra dash kit, adapters and interfaces. While I still have some issues with the interface harness wiring, (radio comes on when plugged in to vehicle harness- with no key on), the new JVC radio powered right up and produced the same tinny sounding, very low volume sound... just like the sound from the OEM GM radio.

I currently have the OEM radio re-installed and scratching my head as to how to proceed with troubleshooting the problem. I'm hoping the symptoms I've described will help someone point me in the right direction.

Thanks in advance for thoughts, comments, questions, or suggestions.

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[dragon.breath 10+ year member]

You could simply have some blown speakers. The only thing that you have working is tweeters. Happens more than you think. Previous owner liked to listen loud, blew a speaker. Then turned the remaining speakers up even louder to compensate. Then blew more speakers till they all were gone.

 

[ZTatZAU]

Thanks for your reply, dragon.breath; and you could be right! But I don't think there were that many speakers to start with. I know there are no speakers in the top of the dash so that leaves two speakers in each front door (one being the tweeter I can hear) and a regular but sadly blown speaker. I'm not sure the rear has any speakers.

Is it possible to check the condition of a speaker (short/open/resistance) or even the existence of a speaker (rear doors?)... by probing the radio connector in the vehicle harness... without pulling the door panels?

I do have the 2007 TB GM radio wiring diagrams (with and without rear Rear Seat Audio) and a multi-meter.

 

[1aespinoza Premium Member]

Is it possible to check the condition of a speaker (short/open/resistance) or even the existence of a speaker (rear doors?)... by probing the radio connector in the vehicle harness... without pulling the door panels?

You said you purchased an adapter harness along with the JVC radio. Remove the OEM radio and plug that harness in. It should be color coded in pairs so testing should be straightforward.

 

[ZTatZAU]

I've already done that 1aespinoza...

So I purchased and installed a JVC KW-V660BT head unit with the various Metra dash kit, adapters and interfaces. While I still have some issues with the interface harness wiring, (radio comes on when plugged in to vehicle harness- with no key on), the new JVC radio powered right up and produced the same tinny sounding, very low volume sound... just like the sound from the OEM GM radio.

... and found the sound was the same as when the original radio was installed. That makes me think the problem is with blown speakers as dragon.breath suggested or broken, shorted, and/or corroded speaker wires.

Still wondering if I can test for these things from the radio connector in the vehicle harness???

ZT

 

[1aespinoza Premium Member]

wondering if I can test for these things from the radio connector in the vehicle harness???

My bad, what I meant is to touch those pairs to a multimeter. Each pair should read about 4 Ohms.

 

[ZTatZAU]

My bad, what I meant is to touch those pairs to a multimeter. Each pair should read about 4 Ohms.

Oh! I see what you mean! Connect the interface harness and do my probing there instead of at the vehicle's connector. Not sure if I'll get to that again as I'm about half done with getting the driver's door panel off.

I'll soon have eyeballs on the LF speaker and also have a new (but old) 6x9 4Ω Pioneer speaker to test with.

ZT

 

[ZTatZAU]

Blown speakers just as dragon.breath suggested! Jumpered up my, wrong size 6x9, test speaker and the stereo comes through loud and clear.

Any suggestions on finding an easy swap speaker set that will bolt right in to my 2007 Trail Blazer? I'm not what you'd call an audiophile and don't need anything fancy, top of the line, or expensive. Just some basic speakers that will bolt right in to the stock setup.

ZT

 

[dragon.breath 10+ year member]

Go to crutchfield.com. They will tell you exactly what fits in your vehicle without modification or what adapters might be needed. Then it’s your call whether you buy from them or search out the same equipment on your own.

 

[ZTatZAU]

Thanks again for your informative replies, dragon.breath!
ZT

 

[ZTatZAU]

My 2007 Trailblazer also has a factory (?) satellite antenna on the roof, just behind the windshield on the driver's side. I'd like to know if this antenna is for Onstar, Sirius XM radio, or perhaps both?

As far as I know the car does not have Onstar and that's fine with me. But my original GM AM/FM/CD (UB0) radio cycles through two XM channels (XM1 & XM2) with the band button. Both of these channels currently play an "XM Preview"... but does this mean the stock original 2007 GM radio is already receiving a Sirius XM signal or has built in XM functionality waiting for a subscription to be purchased?

If so, how can I determine the Sirius XM Radio ID for this OEM GM radio?
I will appreciate any info on this
ZT!

 

[ZTatZAU]

Let me try this question again...

If a GM radio displays and plays two XM Preview channels, does that mean the radio is Sirius XM capable?
If so, how do I determine the GM radio's XM Radio ID to sign up for a subscription?

As for my speaker installation...

Please keep in mind I'm learning as I go here, and I do tend to overthink things, but I'm thinking about impedence. I hope someone can help me with this.

My four new speakers are all Kenwood KFC-651 4Ω speakers... but I noticed that my blown original GM speakers are 4Ω in front and 8Ω in back. I assume the difference is to balance out the separate 4Ω (?) tweeters in the front door speaker assemblies. Is that correct?

So now I'm installing four new 4Ω speakers, all with their own built in tweeters, in the front and the rear. I was planning to disconnect the wires to the original OEM tweeters in the front doors. So the radio will now see 4Ω in each speaker circuit rather than the original 8Ω. Is this going to work correctly?

I appreciate your help!
ZT

 

[1aespinoza Premium Member]

rather than the original 8Ω. Is this going to work correctly?

You're good to go. The tweeter's impedance will not affect the other speaker's impedance in the same x-over network.

 

[dragon.breath 10+ year member]

If you are hearing a XM preview, you have XM radio. Go on XM and hit the information button. It should give you either an id number or a phone number to call. XM can either tell you how to get the id number to come up or in some cases I believe that they can use the vin number for the car to activate a XM subscription.

 

[ZTatZAU]

Thanks again to all who replied here!
New speakers are in, sound good and I can finally hear the XM preview instructions on the OEM GM radio.
I appreciate your help.
ZT