Drive with caution — fix soon.
This code means the computer has detected that bank 2 of your engine is running too rich and it can no longer trim the extra fuel out of the mixture. It's often caused by a leaking fuel injector, high fuel pressure, a faulty oxygen sensor, or a dirty mass airflow sensor. It's a common, fixable code once a technician finds the source of the excess fuel.
$100 – $650
Varies by vehicle and root cause.
Usually yes for short distances, but don't rely on it. A rich condition wastes fuel and can harm the catalytic converter over time, so get it diagnosed within a week or two.
It depends on the cause. Cleaning a sensor or replacing an air filter may be around $100, while a leaking injector, fuel pressure regulator, or oxygen sensor can push it toward $650.
It's moderate. The car will usually still run, but ignoring a rich mixture can lead to fouled plugs and expensive converter damage, so it's smart to address it soon.
Both mean the system is running too rich, but P0172 is on bank 1 and P0175 is on bank 2 (the other cylinder bank). The causes and fixes are very similar.