P0172 is a rich running condition and changing the O2 sensor is not going to help. This is a rather complex code that do not indicate what is faulty. Check the air filter for clogging. If there is a return line for fule system ensure it is not clogged and check fuel pressure. It could be too high.
January, 27, 2013 AT 4:50 PM
I am facing the same problem with Toyota allion for last 6 month.I change O2, filter plug, engine oil sill. But still same old problem. Please give me the complete solution.
January, 27, 2013 AT 7:12 PM
There are no direct fix for this problem as it is an operational malfunction and might not be due to a faulty component. You need to start with basic checks.
Check fuel pressure, injectors, air flow.
Try cleaning the MAF and monitor its operating condition.