P0173Powertrain
Powertrain · SAE
Fuel Trim Malfunction – Bank 2
Meaning
The ECU detected that the short-term and long-term fuel trim corrections on Bank 2 have exceeded the adaptive range. Bank 2 is the cylinder bank that does not contain cylinder 1, and the system is unable to compensate for the air/fuel ratio error on that side.
Common causes
- Vacuum leak at the intake manifold or hoses on the Bank 2 side
- Dirty or faulty MAF or MAP sensor affecting air mass calculation
- Clogged or degraded fuel injectors on Bank 2
- Fuel pressure deviation (too low or too high)
- Contaminated or aged lambda sensor on Bank 2
- Clogged air filter or air leak upstream of the MAF sensor
Symptoms
- Malfunction indicator lamp (MIL) illuminated
- Increased fuel consumption
- Reduced or erratic engine performance
- Rough idle
- Possible smell of unburnt fuel from the exhaust
Severity
Moderata: The vehicle may remain in temporary use, but the issue can cause catalytic converter damage and increased emissions if not resolved.
What to do
- Read and record all stored fault codes and live fuel trim data for Bank 2
- Visually inspect vacuum lines, hoses, and electrical connectors on the Bank 2 side for leaks or damage
- Clean the MAF sensor with a dedicated cleaner spray and verify its operation
- Check fuel pressure at idle and under load using a pressure gauge
- Test injector operation on Bank 2 and lambda sensor function; replace defective components