Fig. 307: Identifying ISO Micro Relay Terminals
Courtesy of FORD MOTOR CO.
2) Check Fuel Pump Relay
Turn ignition switch to OFF position. On ISO micro fuel pump relay terminals that are numbered 1-5,
measure resistance between relay terminal No. 1 and all other relay terminals. Resistance should be 40-
120 ohms between terminals No. 1 and 2 and more than 10 k/ohms between terminal No. 1 and all other
relay terminals. On ISO mini fuel pump relay terminals that are numbered 30, 85, 86, 87 and 87A,
measure resistance between relay terminal No. 85 and all other relay terminals. Resistance should be 40-
120 ohms between terminals No. 85 and 86 and more than 10 k/ohms between terminal No. 85 and other
relay terminals. On both relays, if resistance is not as specified replace relay. If resistance is as specified,
go to next step.
3) Check Fuel Pump (FP) Circuit For Short To PWR In Harness
Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as
necessary. Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground
and FP circuit at fuel pump relay harness connector. See Fig. 299-Fig. 304 . If voltage is less than one
volt, go to next step. If voltage is one volt or more, repair short to PWR in FP circuit.
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline