Bad battery killed chimes and radio

kmpcc05

Member
After replacing bad battery, chimes and radio don't work and dash lights/gauges only come on occasionally during crank but if I press the trip reset or use a turn signal, the gauges will come to life as if the truck was just cranking.

There is absolutely nothing else wrong. Everything functions as it should. This should be a BCM issue right? But I tried a different BCM and it had the same issue. In fact, even before I did a relearn for the new BCM, the radio and chimes already didn't work.

Is there something before the BCM that could be affecting these other functions? I used a meter and there's constant power coming from the BCM to the radio, it's just not sending the signal to turn it on. Is the serial data bus separate from the BCM or is it all the same thing? I used an ACC wire to get the radio working but I'd still like to fix it properly.

At one point, I did a BCM reset by holding the battery terminals together and that caused the chimes to come back.. but when I went to crank the truck, it just clicked. Of course after another reset, no chimes but the truck fired right up. I've never been able to duplicate that since.. this is a devious gremlin.
 

MRRSM

Lifetime VIP Supporter
The Trailblazer OEM Radios may invoke a Security Lock-Out under certain Power Loss or Surge Conditions. The Door "Bong" Chimes are under the control of the Radio so this explains why BOTH have been affected.

There may be some other MORE Specific Radio Security Re-Set Protocols to be found in the instructions documented in the "Glove Box Owner's Manual" ...but give these a shot and see if the "Re-Set" works:

 
Last edited:

Mooseman

Moderator
This is on an '05 Colorado right? It should be close to being the same as on GMT360's.

Is this with the stock radio? If you replaced the BCM, it should have needed a bunch of programming including the VIN and VATS. Replacing the BCM without programming the VIN would disable the radio and could play havoc with a bunch of stuff.

Make sure you have good power, a good fully charged battery with a good clean tight connection. A weak battery or a poor connection can cause all sorts of weird stuff. Checking all your ground points is also a good idea. No idea where they are on this vehicle.
 

MRRSM

Lifetime VIP Supporter
These issues also seem to be intimately related to your other recent post regarding "Loss of Class 2 Network Communication..." in this Thread:

 

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