This is certainly strange. I could possibly see the smaller 650CCA battery not having enough oomph (Sorry about using all these technical terms) when cranking the starter, but it should be more than adequate to power up everything prestart, and allow you to turn off the alarm. I have no idea why the alarm behaved itself when you swapped the bigger 850CCA battery back in there. The alarm should have responded normally with the smaller battery, too.


The magic 12.6V number is basically just forum experience. Nothing official, as far as I know. I don't believe 12.6 itself is even the crucial factor. It's normal for the battery voltage to drop under the massive load of the starter, probably somewhere around 10.0V. I think 12.6V prestart originated as a practical limit to ensure you'd stay above the actual limit with the starter engaged. It's a lot harder to measure the voltage under load, unless you've got a meter with a Min/Max record function to capture it.

One thing you can do is connect a battery charger while trying to start. This will help keep the voltage a bit higher than just a suspect battery alone. If all is good now, you know low voltage is the culprit.

Even if you do find your present battery is at fault, I think you're SOL getting the vendor to refund your money. They have their criteria for testing, and won't put much faith in what some guy on the internet tells ya.

 

Thanks Karl.. I'll get the sensor on thur-fri , install it and dump the codes like other side last yr.. If the transmission doesn't reset I'll have to take it to a trans shop that can program a 6HP26. I' understand there are a few other cars that use them. I think it's one of the most impressive parts of the car.

 

I replaced the right rear speed sensor and all the brake / cruise codes were gone when I started the car, I didn't even have to dump them, even the Trans code was gone..

Then I drove it and the Trans is good too.. I have my car back with $48 part

Thanks everyone

 

Fanjagstic! Congrats