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Oh, one other thing â?? I've noticed now that when I turn the key to ON, the CEL does not light up. Shouldn't it light up whenever the key is ON and the engine not actually running? Would a failure in the same circuit (Ignition?) that uses fuse #4 prevent the CEL from lighting and also prevent an OBD-II system from connecting? Would this same circuit keep the fuel pump from running?




All of these functions require a good F4. Yes, yes, and yes.

F4 feeds the NO terminal of the PCM power relay. PCM power is required to activate the CEL light, turn on the FP, and initiate an OBD-II connection when the relay is energized by turning the ignition switch to RUN or START.

Output of the PCM power relay feeds the O2 sensor fuse (F13-15A), the coils for the AC WOT, FP, high and low speed fan relays, EVAP valve, injectors, IAC, EVR solenoid, VSS, MAF, transaxle, and the PCM.

As you can see, the list of candidate components is pretty long. Additionally, you have all those wiring runs that could have shorted to ground due to wiring insulation failure.

Personally, I'd check to see if recall 99M03 was done or is still applicable first.

Steve

98 Contour SE Sport 2.5 Duratec ATX The wifey's car 89 Taurus SHO - 246K miles 94 SHO ATX - 190K 1997 F-150 5.4L ATX - The Workhorse 150K. ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!