P2503 and passenger side battery overheating

[roberm]

Driving to ATL and "check gauges" light comes on. Thanks to Edge CTS, code p2503 and noticed 11 volts when it formally runs 14+ volts. Found battery passenger side battery overheating and venting steam. Driver side battery was fine; no issue. Replace battery thinking that was the problem but volts still low. Aborted trip and returned home. Volts dropped to 10 along the way back. Parked and inspected the just replaced battery. It had overheated to the point that the top vent cap had blown completely out and was laying loose on the top of the battery case. I'm thinking bad alternator however the one battery overheating has me perplexed. Driver side battery is just fine. Any ideas???

 

[Ozymandias]

Cross over cable as always.

The ECM reads voltage from LH battery but alternator charges RH battery.

If one battery in a parallel system gets overcharged it is always and ever the connection between this two batterys to blame.

Also check the battery pol connectors that they are clean and thight.

 

[sag2]

Cross over cable is bad.

 

[roberm]

Cross over cable as always.

The ECM reads voltage from LH battery but alternator charges RH battery.

If one battery in a parallel system gets overcharged it is always and ever the connection between this two batterys to blame.

Also check the battery pol connectors that they are clean and thight.

Thanks for the detailed explanation! Tightened the crossover cable and no more issues.

 

[Ozymandias]

Thanks for the detailed explanation! Tightened the crossover cable and no more issues.

Great!