OBD-II Diagnostic Trouble Code
P0175 — System Too Rich (Bank 2)
P0175 means bank 2 fuel trims have gone negative beyond the ECM's limit. The ECM is removing as much fuel as it can and still sees a rich mixture on bank 2. It applies to V-engine gasoline trucks. If P0172 is set too, look for a common cause such as fuel pressure, the mass airflow sensor or the evaporative purge system.
Severity 3/5
Less common on commercial trucks
Service this week
Severity
Service this week
System Too Rich (Bank 2)
Code
P0175
Category
Powertrain
Subsystem
Fuel
Truck-relevant
Less common
What this means for truckers
Service within a few days. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
P0175 on the Fuel system is most often leaking injector on bank 2 — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Check-engine light is on. You may also notice poor fuel economy, a fuel smell, black smoke, rough idle and fouled spark plugs on bank 2. A long-term rich condition can damage the catalytic converter.
Common causes
- CommonLeaking injector on bank 2 ($150–$900)
- OccasionalHigh fuel pressure (especially with P0172) ($100–$500)
- OccasionalPurge valve stuck open ($80–$300)
- OccasionalMass airflow sensor over-reporting airflow, or a restricted air filter ($30–$350)
- RareContaminated bank 2 upstream oxygen sensor that reads falsely rich ($120–$350)
How to fix
Check whether P0172 is also set. If both banks are rich, test fuel pressure, the purge valve and the mass airflow sensor. If only bank 2 is rich, test bank 2 injectors.
When to use: First step
Do a fuel pressure hold test to find leakage.
When to use: When fuel trims are worst after startup
Compare the bank 2 upstream sensor with bank 1 using a forced lean test.
When to use: When no real fuel source is found
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0100 — Mass or Volume Air Flow Circuit
- → P0101 — Mass or Volume Air Flow Circuit Range/Performance
- → P0102 — Mass or Volume Air Flow Circuit Low Input
- → P0103 — Mass or Volume Air Flow Circuit High Input
- → P0104 — Mass or Volume Air Flow Circuit Intermittent
Frequently Asked Questions
Can I drive with code P0175?
P0175 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P0175 on a commercial truck?
Total repair cost ranges $30–$900 depending on the root cause. The cheapest fix is usually the first one listed below — Leaking injector on bank 2 — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0175 fail a DOT inspection?
P0175 itself doesn't automatically fail an inspection, but if the truck is in reduced-power mode (limp mode) at the time of inspection, it WILL be flagged. Most inspectors will note the check engine light but pass the truck if it's running and performance is normal. Fix it before a Level 1 inspection regardless.
What's the difference between P0175 and related codes?
P0175 is closely related to: P0100 (Mass or Volume Air Flow Circuit), P0101 (Mass or Volume Air Flow Circuit Range/Performance), P0102 (Mass or Volume Air Flow Circuit Low Input), P0103 (Mass or Volume Air Flow Circuit High Input). These codes share the same subsystem (fuel) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0175 is set without the companions, the issue is more isolated.
How do I prevent P0175 from coming back after a repair?
For P0175 (System Too Rich (Bank 2)), prevention centers on the fuel system. Replace fuel filters at the OEM interval — don't stretch them. Use only diesel from high-volume fuel stops (avoid bottom-of-tank fuel at low-traffic stations). Add a water separator if you don't have one. After repair, prime the fuel system per the engine manual.