OBD-II · Engine and powertrain (P)
P0173
Fuel trim malfunction bank 2
What it means
The ECU cannot keep fuel correction on bank 2 within its normal range. Confirm bank 2's location in the engine's service information.
Symptoms
- engine warning light
- possible rough idle or hesitation
- higher fuel consumption
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | vacuum leak on bank 2 |
| 02 | MAF error |
| 03 | fuel pressure problem |
| 04 | bank 2 lambda sensor fault |
| 05 | exhaust leak on bank 2 |
What to check, step by step
- 01Read short- and long-term fuel trims for both banks: if both are off, look for a shared cause (MAF, fuel pressure)
- 02If only bank 2 is lean, smoke-test the intake on that side
- 03If bank 2 is rich, check the injectors on that bank
- 04Check the bank 2 upstream lambda sensor and look for exhaust leaks before it