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Discussion Starter #1
My engine light came came up and I ran a diagnostic and got the code P0172. engine running rich bank 1.

I am not sure how to go about checking what the cause is. My engine seems to perform the same as it always has. I checked voltage while driving from both sensors in bank 1, sensor 1 seemed to fluctuate a bit while sensor 2 stayed pretty steady. both ranging from 0 to 0.7V.

What should I check? I cleared the code and will see if it comes back.
 

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Had this code out a few times on mine, most times it's been the turbo inter cooler hose has either been loose or torn letting too much air into the system (about £20 off eBay ) the other time I had it the fuel pressure sensor had gone
 

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Discussion Starter #4
I'll check my air filter tomorrow morning, I'm hoping it's something small as I do not want to spend any more money on the car.
 

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Checking the fuel pressurte sensor IS one good item to look at, if there's any fuel in the vacuum line from that to the intake it's shot - and you know how the extra fuel is getting into the system.
 

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Discussion Starter #6
I have driven 100 miles since clearing the code and it hasn't turned back on yet. I ran my diagnostic while driving and exported the log to my email. I'm not sure what I'm looking at with the logging so I'm going to try and see if someone knows what they're looking at to see if any of the sensors are gone.
 

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Discussion Starter #7
If I clear the code, will it come back on if the problem is still occurring? The light hasn't shown again since clearing it.

Also would low pressure in the fuel line cause it to run rich?
 

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No, but high pressure would. If the code hasn't come back, then whatever caused it is no longer causing it. Codes will come back, but some codes are designed to remain until cleared. Due to the mileage, this could be a sign of an O2 sensor going bad. If you notice that your fuel use has gone up, then you will likely want to replace the O2 sensors. I would replace both at the same time, and always purchase OEM sensors. You might want to start the search now to see where you can find Motorcraft O2 sensors at the lowest price. Now if you don't think that you'll keep the car for say 2-3 more years, then purchasing an OEM style aftermarket O2 sensor will probably be ok. We've had a few problems with those failing in short order, but not horrible problems. Whatever you purchase, make sure you get the OEM style, that will come with the same length of wire, thermal insulative wiring cover, and the plug. It typically only costs a small amount more to get the OEM style as opposed to a generic model, but with the generic type you'll have to cut your OEM plug out, and splice the wiring. Please check out advice for changing O2 sensors before you get into it. Sometimes you can get it off with a wrench, but you might want to purchase an O2 sensor socket for your tool collection as that makes it much simpler.
 

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CEL come on fast for a major issue it sees, eventually for a lesser issue that repeats.
 

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Oh, FYI, all O2 sensors fail rich, so as the sensor ages, fuel use goes up. In your situation, the O2 sensor closest to the engine is causing the 2nd sensor to read rich. If the second sensor goes bad as well, you'll run rich without a code, but it will cause your catalytic converter to glow red hot after a short drive, and will eventually ruin it. If the cat is glowing red hot, then it should be replaced also.
 

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Discussion Starter #11
Thank you very much for the help, I logged my diagnostic while driving and there was voltage going through the sensors, the voltage in sensor 1 seemed more erratic than in sensor 2. Now I'm not familiar with this so I'm not sure if it's meant to be that way, I noticed in my mom's mini Cooper that her sensor 1 seemed to jump more than the sensor 2. My sensor 1 seemed to jump a lot more though.

I planned on keeping this car for as long as possible, I've done all the major work to it, timing belt, water pump, wheel bearing, clutch and drop links but I'm sick of putting money in this car. Ive done 40k miles on it and there's 110k miles on the clock.

The light has not come back on since clearing and I've done over 300 miles on it, i calculated my mpg and it seems to be close to what I should be getting (got 38mpg but was stuck in bumper to bumper for over an hour blasting heat).
 

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Discussion Starter #12
Also my car just passed the NCT about a month ago and the emissions were perfect on the car.

Would cleaning the engine bay area and connections with electric cleaner help solve the problem?
My engine bay and connections can be quite filthy
 

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Discussion Starter #13
Just an update I calculated my average mpg from my last fill up and got 41mpg over 390 miles which is pretty much bang on what I would normally get when driving so I don't think my engine is running that rich if it even is.
 
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