Hi,
The PCM is what commands the FPDM. When the key is first turned on, it should actuate the pump for only one second until a signal from the crankshaft position sensor is recognized. If it is running constantly when the key is on and you replaced the PCM and FPDM, there has to be a short to power that is switched.
Okay, this is going to sound odd, but does the pump stop if the PCM power relay is removed?
I'm looking through the schematics and something has to be triggering the FPR. That signals (through the inertia switch) the FPDM. I'm wondering if the PCM power diode is bad and allowing power to back feed.
Inspect the diode. Don't jumper the circuit or install a fuse. Pull the diode and using a multimeter, check for continuity in both directions.
Let me know the results. Note: I attached a pic of the diode's location in the battery junction box. (Pic 1). The remaining pics are from the schematic.
Let me know what you find.
Joe
See pics below.
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Sunday, November 21st, 2021 AT 9:46 PM