1993 Ford F150 F150 Fuel Pumps will not engage

1993 FORD F-150
28,000 MILES • 6 CYL • 2WD • AUTOMATIC
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FENR1S71
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The fuel pumps work fine if connected directly to the battery with jumpers to the sending units, but when in the tanks or otherwise connected through the wiring harness neither pump will engage. The EEC-IV self test code is # 542 "Fuel pump secondary circuit failure PCM to ground" according to the Chiltons manual for the truck. Also when testing the fuel tank selector switch the readings are incorrect. Where do I go from here other than trying to trace every possible wire for shorts?
Jan 2, 2010 at 8:57 PM
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RASMATAZ
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Check and test the fuel pump fuses, fuel pump relay and inertia switch
Jan 2, 2010 at 9:05 PM
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FENR1S71
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Thanks but I did check them and all seem to be working correctly. Is there any other options?
Jan 2, 2010 at 9:07 PM
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RASMATAZ
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Last option here is the computer control of the fuel pump relay
Jan 2, 2010 at 9:37 PM