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Code P1131 1997 Ford LX 3.0 duratec DOHC

02 sensors, cam sensor, fuel runners. coil package, vacuum check - OK, no misfire, injectors OK, PCV replaced, replaced cats, and fuel filter. Still have Service Engine Soon light coming on. Latest scan showed fuel pressure regulator should be replaced. Have spent more on repairs/maintenance than vehicle is worth. Where to now?
Any suggestions are welcomed and would be appreciated. Engnine runs like a champ, idle is smooth no vibs or misses etc, and acceleration is tops, including quick response in passing gear. Cruise at 70 with little or no noise. Some suggestions so far are to ignore SES light. Milage is 187.000 - about half quart low at 3000 to 3500 miles but oil at that stage still looks clear on dip stick. Vehicle has always been serviced properly. Lvee.

This code refers to the 02 sensor. Bank 1 sensor 1 this is the upstream 02 sensor for cylinders1-3.

Two sensors recently replaced. One at lower rear area of radiator and one opposite a catylictic converter toward the passenger side. Also, cam? sensor. Vehicle runs out quick and smooth from stand still and tops 80 mph with no hesitation. The engine idles without any vibration and except for the sound you cannot tell it is running. Could there be a so called glitch in the computerized system that is sending a false positive signal that acuates the SES light? And, how about ignoring the SES light until and if there is some indication of an engine problem using the “ear” method.
Thanks for the comments and your time. Regards. Lveehil.

I’m not familiar with the locations of the 02 sensors on your car, but you’ve probably got 4 02 sensors, an upstream sensor before the catalytic converter (sensor 1 bank 1) for cylinders 1-3, an upstream sensor before the catalytic coverter (sensor 1 bank 2 (cylinders 4-6), a downstream sensor after the catalytic converter (sensor 2 bank 1) cylinders 1-3, and another downstream sensor after the catalytic converter (sensor 2 bank 2) cylinders 4-6. Your code is referring to the upstream sensor for cylinders 1-3. If either of the upstream sensors is bad your gas mileage will likely suffer. The two upstream sensors along with signals from some of the other engine management sensors helps control the fuel trims (amount of gas being fed to the engine). Any mechanic should be able to look at your car and show you where the bank 1 sensor 1 is located The downstream sensors purpose is to verify the catalytic converter is doing it’s job correctly and has nothing to do with fuel trims. If your gas mileage has been low/poor lately it’s probably because this sensor is bad.

-From my tech resource-

P1131 - Ford Type
Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled

Lack of HO2S Switches, Sensor at Lean Limit Conditions

Bank 1 Sensor 1

Engine running in closed loop, then the PCM detected that the HO2S-11 signal did not switch because the fuel control system is at its lean limit

Looking at the conditions to set this code, either your sensor is bad and it is not sending signal to the PCM (Engine computer), there is a wiring problem and the signal is not reaching the PCM, the sensor is good and bank one is actually running very, very lean, or the ever present last option of “your PCM is bad”.

If the sensor has been replaced, it may be an unlikely (Though certainly not impossible) choice. Wiring problems “should” have been checked when the sensor was replaced. (We all know how “should” works)

It’s interesting you mentioned the fuel regulator. What scan indicated it should be replaced. Did you see a low fuel pressure reading?

Response to Meathead 999. I am not savy about this issue, but one of the repair shops did a scan and told replacing the fuel pressure regulator would solve the SES light coming on. I can only say there does not seem to be any fuel feed problem. The car runs as I mentioned above - without any hesitation and accelerates on the money.
Thanks for your input. Lveehil.

Fordman 59. Made notes of your comments and will check with mechanic on them and those form Meathead 999. Thanks to both of you for the adivce and time/effort.

Make: Ford
Model-Year: 1997
Engine: 3.0 duratec DOHC
Model: _________ LX ?


Model: Taurus LX.