What Does P0175 Mean?
The engine is running too rich on bank 2 (or bank B). The ECM has detected that long-term fuel trim on bank 2 is excessively negative, meaning the system cannot subtract enough fuel to reach stoichiometric ratio. Too much fuel or not enough air is reaching the bank 2 cylinders. The driver may notice black exhaust smoke, fuel odor, poor fuel economy, and potentially rough running.
Common Causes
30%
Leaking or stuck-open fuel injector(s) on bank 2 delivering excess fuel
25%
Faulty MAF sensor over-reporting airflow, causing excessive fueling on both banks
20%
High fuel pressure from a stuck or malfunctioning fuel pressure regulator
15%
Faulty bank 2 upstream O2 sensor reporting false lean, causing over-fueling
10%
EVAP system purge valve stuck open, flooding the intake with fuel vapor
Diagnostic Steps
1
Monitor STFT and LTFT on both banks. If only bank 2 is rich, focus on bank-2-specific causes (injectors, O2 sensor). If both banks are rich, look at shared components (MAF, fuel pressure, EVAP).
2
Check fuel rail pressure with a gauge. Pressure above spec indicates a faulty pressure regulator or restricted return line. Many returnless systems use a regulator integrated into the fuel pump module.
3
Monitor the bank 2 upstream O2 sensor waveform. It should oscillate between ~0.1V and ~0.9V. A sensor biased lean (stuck low) will cause the ECM to keep adding fuel.
4
Inspect bank 2 spark plugs. Carbon fouling (dry black soot) confirms rich running. Wet, fuel-smelling plugs suggest injector leakage into the cylinders.
5
Disconnect the EVAP purge valve line while monitoring fuel trims at idle. If trims normalize, the purge system is the culprit.
6
Perform a relative compression or cylinder leak-down test on bank 2 cylinders to rule out mechanical issues that could affect the air-fuel ratio.
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
The engine is running too rich on bank 2 (or bank B). The ECM has detected that long-term fuel trim on bank 2 is excessively negative, meaning the system cannot subtract enough fuel to reach stoichiometric ratio. Too much fuel or not enough air is reaching the bank 2 cylinders. The driver may notice...
The most common cause of P0175 (Oxygen Sensor System Too Rich Fault Bank B) is: Leaking or stuck-open fuel injector(s) on bank 2 delivering excess fuel
Typical repair costs for P0175 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive with caution. Rich conditions wash cylinder walls, accelerate wear, foul plugs, and overheat catalytic converters. A severely overheated converter can glow cherry-red and pose a fire risk. Address promptly, especially if you smell raw fuel or see black smoke.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0175 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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