P0173: Fuel Trim Malfunction — Bank 2
What to do
Expect worse economy and possibly hesitation. Ask whether both banks show the same trim direction; that comparison narrows the cause substantially.
What this code means
Fuel corrections on bank 2 have gone outside the workable range, mirroring P0170. The single most useful observation with any bank 2 trim code is whether bank 1 agrees: a fault on one bank alone points at that bank's injectors, sensor or a local intake leak, while both banks drifting together points at something shared — fuel pressure, the airflow meter, or the evaporative system.
Likely causes
Start here
- Vacuum leak in intake manifold or hoses · moderate
- Contaminated or failing mass air flow sensor · easy
- Faulty oxygen sensor · easy
- Low fuel pressure · moderate
Less common
- Clogged fuel injectors · moderate
- Exhaust leak before the sensor · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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