A couple weeks ago, the car wouldn't start and the dash cluster said "no bus" which I understand is a bad connection between the dash cluster and the ECM, it went away and the car ran fine, well all of a sudden it didn't want to start, has very little power (the horn sounds quiet and the locks are slow, trunk wouldn't even open), if you go to start it all it does it click.

Boosting it it will start, but shows a check engine light, which says low system voltage, and brake circuit a high, or something like that.

Also, the battery jumper cables under the hood tested 13.4 volts, where as my scanner says it's only getting 6.1, so there must be a wiring issue somewhere.

Also, I've posted a video, the speedometer doesn't work half the time, and the traction control light is stuck on, it won't let me turn the traction control off (it doesn't show up as disabled on the dash), and the abs and emergency brake lights flash on and off when the speedo meter drops to zero...

Any ideas anyone??

 

You have figured it out already:

"Also, the battery jumper cables under the hood tested 13.4 volts, where as my scanner says it's only getting 6.1, so there must be a wiring issue somewhere."

Now you're going to have to find it. It's probably a bad ground or a corroded connection "somewhere".

Start at the battery and trace the connections in both directions until you find it. This is not rocket science. If you have a multimeter and some patience you can find the problem using a logical approach. When you succeed, come back and tell us about it.

 

How old is your battery?