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sprinkles08
sprinkles08, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 22670
Experience:  ASE Master & Advanced level certified, Chrysler Master Certified, Trans and Hybrid Specialist
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2005 300 base 2.7l battery was dead.. replaced along with

Customer Question

2005 300 base 2.7l battery was dead.. replaced along with alternator. When I reconnected battery everything in the front control module turned on. Wipers, horn, lights, radiator fans, etc.. I swapped the PCM with 3 others known reasonably good and the same problem occurs when I reconnect the battery. No dash display, nothing when I turn the start key and cannot read any codes.
Submitted: 1 year ago.
Category: Chrysler
Expert:  sprinkles08 replied 1 year ago.
Hello and welcome to JustAnswer!
It sounds as if one or both communication bus networks is down. The modules all communicate on two separate two wire networks. If the front control module can't communicate then the lights and wipers will come on for safety, if it isn't communicating with the PCM then the cooling fans will run.
The problem may be in the FCM itself or it could be a wiring issue or failure in another module. I'm wondering if reversed polarity damaged the module.
Do you have an actual scan tool capable of communication with all modules?