94 F150 throwing code 542
I need some ideas. I replaced my clockspringyesterday to fix a not working horn (now works), following all the typical protocols like unplugging the battery and wiring and dismantling and re-mantling yada yada...Anywho. Finished up, turned the truck and it wouldn’t turn over. When I try to start the truck up it’s getting battery power and air but it doesn’t sound like it’s getting fuel pressure. Check engine light came on. I ran the Key On Engine Off Test and got the EEC Code 542: Fuel Pump Secondary Circuit Failure. I checked the Fuel Pump Shut-Off switch. It was as it should be, all the way down. Unusual as it seems my fuel pumps haven’t had any issues (I think the guy before me replaced them). They don’t drip or have any signs of issues. None of the fuses seemed to be burnt. Could they look fine and not be? Could I have short circuited something? Could it be coincidental? Broken/bad wire, fuse, or a bad sensor or pump unit?
Anyone got suggestions? I’m a little frustrated at the sheer volume of overreacting my truck seems to have to now having a working horn 😂
Sounds like you're fuel pump relay is faulty.
Test 1: swap your horn relay with your fuel pump relay.
Does it work now?
Test 2: use the eec-iv test connector to force the fuel pump relay on by jumping the fuel pump test terminal to the metal hood hinge bracket or any other ground. With the ignition switch in the "run" position, your fuel pump should run constantly.
Can you hear the fuel pump running constantly?
Sounds like you need a new fuel pump
Cycle the key on and off 75 times and see if it will start
Go ahead and do the pinpoint test steps foe code 542 in the PCED
Here is a sample, you can get them from AllData for free at your library
But you will notice on J25, that power runs through with the HEGO heater circuit
That is why I ALWAYS say to at least look at, (if not perform) the pinpoint tests
You can scratch your head for days without them










