2005 V6 Convertible.

I'm having some strange electrical issues that appear to happen more often when the weather is warm. Initially I noticed the aftermarket radio powering off and coming back on occasionally. I figured it was a radio issue. I let my sister borrow the car for a few weeks and she reported more issues such as the headlights flickering, and check charging system message on the instrument panel. Since getting the car back and driving it myself, I didn't have any issues for a couple of weeks, but then I had intermittent issues with the following:

Check Charging System, Fuel Level Low, and DTE ODO Data Error all displaying on instrument cluster.
Windows not working
Door locks not working
Radio not working
Blinkers not working
A/C not working
B1556 and U1900 showing as fault codes on OBD2

The battery is less than a year old and my OBD2 shows consistent charging from the alternator.

I checked the grounds in the engine compartment and checked the connections to the computer. No signs of corrosion.

I'm totally stumped and looking for ideas on where to start looking. Again, these issues are intermittent and don't always happen at the same time.

I tried searching for anything similar and the best answer I could come up with was replace the alternator and I'm pretty sure that's not the issue.

Any advise would be greatly appreciated.

Thanks,
Nathan

 

Most likely the SJB got some moisture in it. It is located in the pass. kick panel. Feel around the pass. side carpet if it is damp or wet. The cowl drains maybe clogged and water will overflow on the pass. side carpet.