I saw one thread on here where this question was posed, but saw no replies. I wonder if I'll have better luck.

I've had my share of issues with this car. It currently is right around the 92,000 mile mark. And over the last three months, I have done a ton to get it not only to pass inspection, but to hopefully get it to a point where my miles per gallon increased. Currently I'm getting about 15 for city and about 18-20 highway. Now in peak condition, this car with this engine is supposed to get upwards of 18 city and supposedly 27 on the highway.

Sorry for the short story to start. My issue is this. I still have a 542 code when I take a reading. Fuel pump circuit open connection - Electronic Control Assembly to motor ground. Now interestingly, I recently had the code 543 pop up which is essentially the same only it was to the battery. I had purchased a fuel pump expecting to have to change it. Thing is I never did. Before we even got that far, I replaced the terminals on the battery and that code disappeared along with all of the others.

I thought my problem was solved, but 542 returned and I while I'm not afraid of messing with wires, I wonder if anyone that frequents this site has had a similar issue and can shed some light on how I tackle this. I feel like this is the last hurdle I have to cross in order to get this car to stop puttering and eliminate the error messages once and for all. I don't believe the fuel pump is the issue considering the new terminals resolved the other code. I think it has to do with the actual motor ground or something in the Electronic Control Assembly.

Any help would be IMMENSELY appreciated.

Many thanks,

Robby - Owner of 1993 Ford Taurus, 3.8 L engine.

 

KOEO (Key on, Engine Off)
542 - Fuel Pump Circuit Open; ECA to motor

KOER (Key on, Engine Running)
173 - Oxygen Sensor Indicates Rich Condition, right side
137 - Indicates Rich Condition, left side
129 - Insufficient Manifold Absolute Pressure/ Mass Air Flow Change
167 - Insufficient Throttle Position Sensor change

 

The IAC should be physically removed and cleaned. You'll need a new gasket, of course. These engines were known for leaky fuel pressure regulators which could explain the rich condition. With the engine warm and shut off, pull off the vacuum line going to the fuel pressure regulator. If there is any fuel present, it's bad. The MAF sensor must also be removed for cleaning. Carb cleaner can be used for the IAC, but MAF cleaner should be used for it. Both can be cleaned with the MAF cleaner which is available at most any parts store. The throttle position sensor can be checked with an ohmmeter. Watch for any 'glitches' in resistance from idle position to wide open throttle. From the symptoms, I'd look very closely just off idle. The inertia switch is either on or off. If it were faulty, you'd have no power going to the fuel pump. Does the engine seem to run okay when it's cold? Problems begin after warmup? If so, sounds like a flooding issue, to me.

 

I believe your vehicle has an IRCM, (Integrated relay control module) and it should be located under the radiator cover right in front just behind the grille opening.
It contains relays for EEC Power, fuel pump, cooling fans and A/C.
The module has a plug with many wires going to it. You might try removing and installing the plug since there could be a poor connection there.
Ground connections are very important and you might start at the battery negative post and check any and all grounds you can find and see including those under the vehicle that may provide the ground for the fuel pump.
Just looking at them does nothing!
You have to loosen them and move them around and retighten them.
Try that and see if it doesn't help get rid of that code and also might very well improve your MPG.
Also , as someone mentioned in an earlier post, make sure the connections at the inertia switch are good because with that system the wiring from the switch goes to ground.