PO172 Bank 1 System to rich

davolvo · Post by **davolvo** » 10 Apr 2012, 07:52

Hello, I hope I am not bothering you guys with a topic that has already been addressed but when I searched I only came up with info relating to model 850.

My check engine light came on and when I had it scanned it came up PO172 Bank 1 System to rich. A few weeks ago, for one day only my car was difficult to start since then no issues. It idles fine, there does not seem to be any unusual fuel odors and gas mileage is good. I do need to change my plugs (30,000 miles now) and I am sure something needs to be cleaned out. Would a gas treatment work? Or am I way off base here? Guess I am just praying it is something simple. Thanks for any advice you may have.

Post by **billofdurham** » 10 Apr 2012, 11:49

P0172 equates to Volvo code EFI 231, long term fuel trim part load or EFI 232, long term fuel trim idling.

I have no specific repairs listed for these but there are several things that can be checked/cleaned:
Intake/exhaust leak.
Fuel pressure.
Excessive fuel in engine oil.
Engine oil level too high.
Injectors.
EVAP canister purge valve.
Heated oxygen sensor.
MAF sensor.
Engine Coolant temperature (ECT) sensor.

I would start with the last two.

The ECT can be checked with an ohmmeter or multimeter. Readings should be as in the attached:

960 ECT test.pdf: (133.66 KiB) Downloaded 712 times

The MAF sensor can also be checked with a meter:

960 MAF testing.pdf: (311.93 KiB) Downloaded 545 times

The MAF sensor can also be cleaned with a cleaning spray.

If the code hasn't been erased the ECU will still compensate for the fault code and even after cleaning/checking the code will still be there. You must erase it.

Bill.

davolvo · Post by **davolvo** » 11 Apr 2012, 08:40

I am sorry, but what is MAF? (I am a girl) and how would fuel get into my oil? Geez, it has been such a good little car I hope I am not on the verge of something serious here. I can't afford to replace it.

Post by **jblackburn** » 11 Apr 2012, 08:52

P0172 is almost always a vacuum leak on the 5 cylinder cars. I would suggest inspecting all vacuum lines for cracking or broken lines. Spraying A can of carb cleaner will help you find leaks when the engine idle revs up.

If you can't find anything, you can have a garage perform a smoke test on the intake system.

Post by **billofdurham** » 11 Apr 2012, 12:12

I am sorry, but what is MAF?

MAF = Mass Air Flow sensor. It is a sensor mounted between the air filter housing and the throttle body. It measures the barometric pressure, humidity and temperature of the incoming air and sends the information to the control unit to assist in regulating the fuel flow.

960 MAF location.pdf: (149.04 KiB) Downloaded 444 times

This is easy to clean using the correct MAF spray cleaner. Do NOT use carb cleaner.

Fuel can get into the oil if the control unit is receiving false information from any of the sensors. This can lead to the control unit pushing more fuel through than the engine needs and it has to go somewhere. Down into the oil is the easiest path.

When you had the codes read did the person reading them erase the code? Sometimes a code will be set by a momentary glitch in the system. Until the code is erased the control unit will compensate for it. My first line of attack when a code is set is to erase it and run the car to see if it returns. This often proves to be the solution.

(I am a girl)

So is my daughter and she wields a mean wrench, so keep asking your questions - we shall help all we can.

Bill.

davolvo · Post by **davolvo** » 12 Apr 2012, 08:17

Ok thank you, I downloaded the .pdf links and will check everything one at a time. Thank you, thank you, thank you!

A girl

Oh, I can turn a wrench, I just don't know all the lingo..