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Hi All: I'm a 30 year guy at a Ford dealership. I get all of the weird stuff. I don't know where to post this where it will get seen by anyone that might have an answer. Admin please move this to a more appropriate area if needed, Thanks! I'm trying to fix this 2011 BEV. It had a bunch of codes related to the battery pack. They all cleared, but it won't connect. It makes code: P0C78 - HV battery system pre-charge time too long. There are no pinpoint tests left on the archive. I see some of you adventurous types have bought the DMOC 645 units for your own purposes. I read the documentation posted somewhere on this forum, and it seems to indicate that the pre-charge IGFETs and capacitors live in the DMOC. Some preliminary testing on the Transit Connect shows that when you turn the key to the 'start' position, the contactor in the battery turns on for a couple of seconds and there is 350V present in the junction box bus-bars during that time. The contactor drops back out, then you get a red triangle lamp, a turtle lamp and the charge indicator stays on. It sets the pre-charge code. What I'm trying to find out, is if there is another contactor inside the DMOC. Does anybody have a good working knowledge of this unit that could point me in the right direction? Thanks for your time! Grant
 

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There is no pre-charge relay in the DMOC645, it is in the battery pack...

When the VCU turns on the pre-charger it is looking for the voltage sensed in the DMOC645 (capacitors charging) to be equal to the voltage sensed by the BMS.

Then when they are near equal, the contactor in the battery pack closes.

The error message is saying that the VCU timed out waiting for those voltages to be equal, so something is loading down the DMOC645 (probably inside the controller, since you can measure voltage is being supplied to the DMOC645).


I would use CCshell and connect to the DMOC645 and check and see what it thinks the voltage is...

It might have a blown fuse, internal power supply is damaged, capacitor has shorted, or the voltage sense circuit has failed.

Hope that helps,
Wolf
 
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