Understanding P0175 on the 2017 Honda Accord
The P0175 code on your 2017 Honda Accord means the ECM has detected a rich air-fuel mixture on bank 2. The 2017 Accord (9th generation) offers three engine options: the 2.4L i-VTEC inline-four (185 hp), the 3.5L i-VTEC V6 (278 hp), and a 2.0L hybrid. The P0175 code is most directly relevant to the 3.5L V6, which has a distinct bank 2 cylinder group. On the 2.4L inline-four, the ECM may still use bank 2 fuel trim monitoring. At 7-9 years old with potentially 80,000-130,000 miles, wear-related failures are the primary suspect.
Symptoms of a Rich Running Engine
- Check engine light on steadily
- Strong gasoline smell from the exhaust
- Black soot at the tailpipe
- Rough or unsteady idle
- Fuel economy drops well below the rated 23–34 mpg
- Engine stumbles or hesitates
- Possible fouled spark plugs causing misfires
What Causes P0175 on the 2017 Accord
1. Aging O2 Sensor (High Likelihood)
The oxygen sensors on a 2017 Accord with 80,000+ miles have likely reached the end of their effective lifespan. A degraded sensor that responds slowly or reads biased will cause the ECM to miscalculate fuel delivery. On the 3.5L V6, the bank 2 upstream O2 sensor is critical for real-time fuel trim corrections. On the 2.4L, the primary O2 sensor serves the same function. Replacing the affected O2 sensor is often the simplest and most cost-effective fix.
2. Leaking Fuel Injectors (Medium Likelihood)
The 2017 Accord's 2.4L uses port fuel injection, while the 3.5L V6 uses Honda's i-VTEC with port injection as well. Over years of service, injector O-ring seals can harden and crack, allowing fuel to drip or spray improperly. A leaking injector delivers excess fuel to its cylinder. On the 3.5L V6, a leaking injector on bank 2 (cylinders 1, 2, 3 on the rear bank) specifically triggers P0175. Pull and inspect the spark plugs — a wet, fuel-fouled plug identifies the problematic cylinder.
3. Fuel Pressure Regulator Failure (Medium Likelihood)
The 2017 Accord's fuel pressure regulator is a mechanical diaphragm-style unit on the 2.4L. After 7+ years, the diaphragm can deteriorate, causing fuel pressure to run high. A classic diagnostic trick: disconnect the vacuum line from the regulator and check for fuel in the line. If fuel is present, the diaphragm has failed and fuel is entering the intake. On the 3.5L V6, check for similar symptoms at the regulator on the fuel rail.
4. MAF Sensor Contamination (Low Likelihood)
Years of oil vapor from the PCV system can contaminate the MAF sensor, but typically this causes lean codes rather than rich. However, if the MAF is overreading due to an electrical fault or specific contamination pattern, it can cause the ECM to inject excess fuel. Clean the MAF sensor as a low-cost diagnostic step.
Diagnostic Procedure
- Identify your engine — The diagnostic approach differs between the 2.4L four-cylinder and 3.5L V6.
- Scan for all codes — P0172 alongside P0175 on the V6 means both banks are rich (systemic issue like fuel pressure).
- Check fuel trims — LTFT below -12% on bank 2 confirms the ECM is cutting fuel heavily.
- Test O2 sensors — Monitor switching frequency. Sensors should oscillate 6-8 times per 10 seconds at steady cruise.
- Inspect fuel pressure regulator — Check the vacuum line for fuel and test fuel rail pressure against Honda specifications.
Repair Costs for the 2017 Accord
- O2 sensor replacement: $80–$230
- Fuel injector replacement: $100–$300 per injector
- Fuel pressure regulator: $120–$280
- MAF sensor replacement: $80–$200
- Spark plugs: $40–$80 (four-cylinder) or $80–$150 (V6)
DIY Friendly
The 9th-generation Accord is very DIY-accessible. O2 sensor replacement is a beginner-level job on the 2.4L and intermediate on the V6 (the bank 2 sensor on the V6 is at the rear and can be tricky to access). Fuel injector replacement on the 2.4L port injection system is straightforward. The V6's rear bank injectors require more disassembly. The fuel pressure regulator test is a quick check that any DIYer can perform.
Don't Delay the Fix
At 2017's mileage range, the catalytic converter is likely past its prime. Running rich accelerates catalyst degradation and can push it over the edge into failure. Catalytic converter replacement on the V6 Accord runs $800–$2,000, and in states with emissions testing, a failed catalyst means a failed inspection. Fixing P0175 promptly is significantly cheaper than replacing catalytic converters.