Does anyone know what a 543 code means on a 93 ford explorer (OBD-I). My book says something about a Open circuit connection between my fuel pump and my ECA (Electric Control Assembly), BUT I haven't a clue what that means. Help please?

 

I have to admit I'm somewhat confused by this question. My understanding of the Ford EEC (electronic engine control) systems tells me that for first generation explorers (1991-1994 or 1995) the EEC-IV was used. Later models (1995-present) used the EEC-V or more commonly called the OBD-II (onboard diagnostics). The codes for the OBD-II systems use the POXXX number format. The EEC-IV (earlier models) use either a 2 or 3 digit (numeric only) fault code, depending on year and model. The manual I have for my OBD-II code reader doesn't list the PO543 code...but it shouldn't give that code if your Explorer is a '93. Double check the year of the vehicle shown on the sticker on the drivers door, or question the source of the code you're getting. I'm sure you're getting bad info from one of these. If it is indeed a '93, here's how you can pull your own codes:
http://www.explorerforum.com/forums/...d.php?t=147734
follow the link inside the article to see how to hook up a voltmeter.

 

Sorry it's an OBD-I and the code is a 543 code.

 

The info I have...and it's not all that good...says the code 543 shows an open fuel pump circuit between the Battery and EEC. All I see on a diagram in that circuit is the fuel pump relay, a 20 amp fuse, and the inertia switch...and of course, wires.

 

I know lots of wire. I guess I've been avoiding it I really was hoping it was a simple as changing the pump, now..... I guess it's a fu**ed upwire huntin' I go, hey?