2006 5.9 engine stalls

[AStewart]

Engine stalls when grid heater kicks in. Batteries are new. Dealer replaced the valve cover gasket under warranty when it ran poorly in the past like this. Disconnect grid heater hard start cold but once it is warm it runs good all day. Could it be the valve cover wires again?

 

[sag2]

What is the actual battery voltage on BOTH batteries when it dies?

All battery connections and grounds clean and tight?

 

[AStewart]

The batteries are new. The grid heater drops the volts to 11.9. Something is reacting to the lower voltage. ECM or wiring harness.

 

[sag2]

If battery voltage is dropping into the 11's you have a problem. You need to confirm the batteries are indeed good by having them tested. Then you need to confirm all connections are clean and tight. That includes PDC and ECM connections as well. There are thousands of trucks out there under similar conditions that do not die when the heaters come on.