1990 2.3L ford mustang-hard fault code 54, replaced IAC sensor and ACT sensor, wiring looks ok, start vehicle-within 10 seconds-idle drops and check engine light comes on- code 54. Cleaned TB and ISC,egr, intake and code keeps coming back. What else can be causing this code- bad ecm? No other codes, vehicle runs good otherwise. Vehicle has 80k miles

SOURCE: 96 Ford truck engine lIght will not go away.

this is the problem with code readers they bwill tell you the code and sometimes even have a reset feature. However they do not tell you the parameters and don't have an drivability feature so you can not test the ecm and all the sensors or modules while engine is running. diagnostic scan tools are very expensive and hard to use unless you have been trained to do so and PEP BOYs is not what I call real reliable mechanics to begin with. Now I concure with toddG on his reasoning in what might be the potential fault. if your vehicle is running rich or lean your O2 sensor will pick this up on the exaust side, however it is not the sole sensor responsible for the ecm adjusting the fuel air mixture.. you stated that you have switched out several o2 sensors and the fuel pressure regulator, but there is also you mass air flow sensor, your TPS sensor, as well as your map sensor these are worth checking out and just because a faulty sensor is the problem doesn't mean you will get a code each time. the system is built with redundancy in order to keep the vehicle running. in order to get the best possible diagnois take it to a shop where they have a full diagnostic scanner this will have not only OBD1 and OBD2 but cam protocol as well. while the tech is scanning the vehicle he will be able to see how the engine is performing under realtime conditions. please rate this as well as change the rating for toddg because he did offer a valid suggestion

SOURCE: codes 171 and 174 2001 ford winstar

dont take soo much in consideration after you have make all this things, some time is on only for any wire faulty, or a shrt electrical arc in any place in wire system. ask auto tap mechsnics for this maybe they have similar case before.

Harvey N Tawatao

• 3854 Answers
• Posted on May 01, 2009

SOURCE: PO174 HOW TO CLEAR THE CODE

Okay so the more oxygen in the exhaust (lean condition) the lower the voltage from the O2 sensor and the more fuel the computer calls for. Then the oxygen content in the exhaust drops (because it is being used up in the combustion process), and the voltage increases (rich condition) and the process repeats, for as long as the car is running, hundreds of times a minute. A gasoline internal combustion engine needs oxygen to burn the fuel. If the mixture is ideal (or 14.7:1) then all of the oxygen is consumed as the fuel is burned. The exact amount of fuel needed to produce a 14.7:1 air/fuel ratio varies with barometric pressure (altitude), relative humidity and fuel quality and condition; thus the need for oxygen sensors.

So knowing all of this what should we check when we have those pesky rich or lean codes? The most common issues for lean codes are:

1. Vacuum leaks - check for failed or loose vacuum lines, leaking intake gaskets, intake air tubes loose or any other source of un-metered air leaks (leaks after the Mass Air Flow Sensor) 
2. Restricted fuel filter or bent/pinched fuel system lines 
3. Incorrect input from other sensors, such as the Mass Air Flow Sensor, which may not always drop a separate code 
4. Engine misfire – Yes I know this one may seem weird. You might think that if there is a misfire then you will have all that unburned fuel and it should read rich; right? Well the O2 sensors read only oxygen content in the exhaust, so if you have all that unburned fuel from incomplete combustion then, you guessed it, you also have all that unburned oxygen. High O2 content in exhaust equals a lean reading!

There are also some other possibilities such as an internally leaking EGR system, (but this will typically set a separate code). A leak in the exhaust system before the O2 sensor will also cause incorrect readings. And always check for after- market modifications. These can throw a wrench into the works! The only other possibilities (however unlikely), are wiring issues, computer concerns or a bad O2 sensor!

P0174 is a Lean condition on the side of the engine where cylinder # 2 is. Good luck and hope this helps.

SOURCE: Can't fix the EGR excessive flow code

In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.

• Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticeable difference in RPM's with the EGR open

• Clean out the EGR valve and/or tubing to remove deposits
• Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
• Replace the DPFE sensor (with a good quality / OEM one)

SOURCE: Greetings, I have a 2001

Unfortunately there are several things that code could mean. Unless you still have the number code, it's hard to say. What is not hard to say is that, Ford should have caught that and addressed it in the immediate repair. Sounds like they got all the easy stuff in hopes that you would come back and spend more money. If there is a "check engine" light on, there is an issue and should be checked out and repaired. My first call would be to the Service manager of the dealer and kindly explain the issue that the technician MISSED. If he can't do anything, talk to the General manager. Let me know if you need anything else.