Drive with caution — fix soon.
This code means the computer has detected that bank 1 is running too rich, with more fuel in the mixture than it should have, and it can no longer trim it back to normal. Common causes include a leaking fuel injector, high fuel pressure, a faulty oxygen sensor, or a dirty mass airflow sensor. It's a common code and usually fixable once a technician pinpoints why the mixture is too rich.
$100 – $650
Varies by vehicle and root cause.
Usually yes for short trips, but it's not ideal. A too-rich mixture wastes fuel and can foul spark plugs or harm the catalytic converter, so have it diagnosed within a week or two.
Simpler fixes like a new air filter or cleaning a MAF sensor may cost around $100, while replacing a fuel injector, pressure regulator, or oxygen sensor can run up to about $650.
It's moderate. The car typically still drives, but a rich condition can damage emissions parts and waste gas, so it's worth fixing promptly rather than ignoring it.
Running rich means there's too much fuel and not enough air in the mixture. The computer normally trims this out, but a P0173 means the imbalance is beyond what it can correct.