I have a '00 Tahoe 5.3L that gave me some trouble last night. It was parked 4 days over the weekend and when I got in it threw two codes while driving: P0230 and P0404. The truck seemed to run fine but the volt meter seemed low. I hooked up my bluetooth scanner and monitored the voltage with that. It read 12.9-13.2 volts. Am I crazy or is that low? Normally my volt gauge reads near dead on 14 volts. Could my alternator be going bad or is this all in my head?