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I recently recieved an engine code of
543 Fuel pump secondary circuit failure Battery to control module Does anyone know if I need to replace a battery on the PCM or the whole PCM? Any help will be greatly appreciated, thanks
The computer monitors the switched side of the relay; the wire that goes to the fuel pump to make sure that it is getting voltage and basically verifies that the fuel pump relay is working. It could be an intermittent fuel pump problem or something else. I would clear it and see if it comes back. Nothing really needs to be replaced just yet. I think also that this code can be set by switching tanks while the truck is running, but I don't know for sure.