Ive had electrical problems for about 2 months,ofcourse I havent driven it since it snows but first ill explain how my problem all started:
I went out one morning while it was still warm out and I have never had a problem starting the car since ive owned for about 4 yrs, the battery was almost completely dead except it barely had interior lights but not enought to turn the car over(the Battery was bought brand new in early spring last year).I jumped the car and it turned right over but I noticed I didnt have dash lights while it was running but I had dash lights if I turned on the parking lights,I got a code for left and right mirrors circuit and cleared the code and It didnt come back ,fast forward to today , i started it up to run it for a few minutes and shut it off and checked for codes and got BO605- which is (BCM internal memory malfunction. where do I start to look ?any help would be greatly appreciated

 

I wouldn't be too concerned about it. Reset it and see if it comes back. Just one of the many electrical gremlins that pop up and go away. Did it have a H or C beside it?

Get a trickle charger. These cars are notorious for killing batteries.

If you felt froggy cleaning grounds may be a good idea.

 

You will soon learn (hopefully not the painful way) that C5 & C6 cars DO NOT LIKE LOW SYSTEM VOLTAGE!

When you subject some of the modules to voltage surges, low voltage, moisture, etc.. they become VERY UNHAPPY and sometime throw DTCs and some have been known to outright FAIL.

Many of us on here have seen several relays in the system fail due to operating at under voltage situations.

Here is my recommendation:

When your battery is dead or very low,, ALWAYS disconnect it from the car and use a battery charger to fully charge it. Once it is fully charged, reinstall it, properly torque the terminals back on and then turn on the ignition and check for DTCs. Its recommended that you have seriously discharged batteries fully tested to make sure that they are not damaged and can maintain a proper charge. Have the battery checked for proper Cold Cranking Amps and RESERVE CAPACITY.

NOTE!! Reconnecting the battery to the car FREQUENTLY cause modules to set random DTCs. I ALWAYS clear ALL the codes after a battery reconnect and then MONITOR from that point.

SO,, ALL that said; recharge the battery, reconnect, clear the DTCs and see what you have after that.

You alternator is designed to MAINTAIN the charge on the battery. Although it can recharge a dead battery after a JUMP START; IT IS NOT DESIGNED to charge a dead battery back to full charge.

It takes 5-6 hours or longer to properly charge and top off a dead battery. I'm fairly sure that you don't normally drive that long after a emergency jump start.

ANOTHER note of interest.

Something that I have see happen several times in the past.

NEVER EVER connect a battery charger or maintainer directly to the car WITHOUT battery connected to the car. Battery chargers output a DC SQUARE WAVE! NOT PURE DC like the battery outputs. If you put a square wave DC power supply into your C5's electrical system, you could be in for a really expensive repair bill.

When you connect a charger to the battery while its connected to the electrical system, the battery acts like a buffer and the electrical system does not see the DC Square wave.

IF,,,,,,,,,,,, the battery is DEAD, you have much less BUFFER and can damage things. Its always recommended to disconnect the NEG battery cable and charge the battery out of circuit.

Bill