Fuel Trim Malfunction (Bank 2)

The engine is trying to adjust fuel delivery for bank 2 but is unable to do it properly, leading to inefficient fuel usage and possible poor running conditions.

The powertrain control module (PCM) monitors the air-fuel mixture in the engine. If the long-term or short-term fuel trim for bank 2 remains outside of the expected range, it throws the P0173 code. This means that the computer is trying to adjust the fuel delivery by more than about 10-25% from the ideal mixture.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check for any vacuum leaks around the intake manifold and hoses connected to bank 2. Repair as needed. Decision: If leaks found, fix and retest. If no leaks, move to step 2.
2. 22. Inspect the fuel injectors on bank 2 for clogging or electrical issues. Measure resistance across the injectors; should be between 12-16 ohms. Decision: If faulty injectors, replace and retest. If they check out, move to step 3.
3. 33. Test the fuel pressure using a gauge; it should be within manufacturer specifications (typically 35-65 psi). Decision: If pressure is low, check the fuel pump and regulator. If pressure is good, move to step 4.
4. 44. Check the MAF sensor; clean it if dirty and verify proper operation with a scan tool. Decision: If MAF is faulty, replace it. If MAF functions correctly, move to step 5.
5. 55. Look for exhaust leaks near bank 2 that could skew O2 sensor readings. Repair any leaks found. Decision: If leaks are fixed but code persists, consider PCM or sensor issues.

• Vacuum leaks on bank 2
• Faulty fuel injectors
• Exhaust leaks affecting O2 sensor readings
• Faulty mass airflow sensor (MAF)
• Bad fuel pressure regulator or fuel pump issues

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