Originally Posted by
DmaxMaverick
Disconnect BOTH batteries completely, ground a Batt+ cable to chassis for 30 minutes. This should clear any odd errors in the system. Reconnect ONLY the LEFT battery, until both can be replaced. Connect the Batt+ cable to the bad battery, but leave the ground open and secured out of the way (prevents incidental grounding, and secures the duplex connector). One bad battery can take down the entire system and play havoc with the computers. One healthy battery will do fine during moderate climate. I ran my 2001 with only one Yellow Top for nearly a year after the other died (after about 10 years) before replacing both. I would not routinely recommend this on a 2003+ model (significantly more complex electronics), but in a pinch...