You really should scan for the code that is causing the cel. I don't think a weak battery would trigger a cel.
Also, removing the faceplate shouldn't make a difference if the stereo was installed properly. There are typically 2 power feeds to the radio. The main power is on when the truck is keyed on and then there is a constant power feed that is a very low draw to maintain radio settings and presets and such. When you turn the truck off, if the radio turns off, then removing the faceplate will not help any further.
Now, I see that you have a Sony head unit. I recently helped a member of the golf cart forum I go to that just put a Sony deck on his cart and he said the faceplate stayed lit even when he pushed the power button to turn it off. Turned out it was a "feature" of the radio and in order to turn the unit off completely, he had to hold the power button for 2 seconds. His unit also had a function to set it to auto-power off after an amount of time. All that said, a cart install and a vehicle install are different in that the main power on a cart is usually not keyed so the radio doesn't know when power should be off. However, I have seen people install car radios and just tap a 12v source that is not keyed and forces you to have to turn the radio off manually.
Not sure how any of this could be related to your cel but having the code may help clear that up.
Last edited by 04HemiGreg; 04-25-2013 at 11:16 AM.