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Ford Explorer DTCs P0171 And P0174

Q. I am helping my son work on a 1997 Ford Explorer with a 4.0 liter SOHC. I have a scan tool which shows P0171 and P0174 which are lean conditions on both engine banks. My scan tool has many more functions, including graphs and meters, Auterra brand for PALM OS. I used these features to look at different sensor interactions under load and at idle.

Ford Explorer DTCs P0171 And P0174

Both O2 sensors are at 0 volts but I think that is where they should be with the engine running lean. I have access to lots of information but am having trouble analyzing it to get to the root cause. There has been new Mass Air Flow Sensor installed but the trouble codes returned and the symptoms remain.

Those symptoms are: Rough Idle and stalling. A list of what sensors generate what codes would be great. Is there a good reference book for this kind of stuff, more than just a trouble code list? Any help would be appreciated.


A. Here is the relevant information for the P0171 and P0174 DTCs.

Ford Explorer DTCs P0171 And P0174

As for a comprehensive book on what could cause a particular code, I don't think you will find one. So many different things can cause, for example, the DTCs you are getting. And that these things change from year to year, make to make, model to model and engine to engine, it would be almost impossible to compile such information.

The best thing to do is get the factory service manual for your particular vehicle since it will contain all the information specific to that vehicle.

Take a look at the information in these articles. I think, even though it's new, the MAF could still be the problem.

Ford F150 Codes P0171 & P0174

Ford Expedition P0171 & P0174

Ford Mass Air Flow Sensors

Additional Information provided courtesy of AllDATA

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