# P0175: System Too Rich (Bank 2) **Verdict:** Drive to a shop this week Fuel and air metering - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $15-$1,200 - **Urgency:** This week - **Most likely:** MAF sensor, fuel pressure or injector - **DIY?:** Steps 1-2 ## Quick answer P0175 means bank 2 of a V6 or V8 engine is running too rich, with more fuel than it can burn, and the computer cannot pull enough fuel back. If P0172 is also set, look for a shared cause like the MAF sensor, fuel pressure or purge valve. ## What does P0175 mean? On engines with two banks of cylinders, such as V6, V8 and flat engines, each bank has its own upstream oxygen sensor and its own fuel trims. When the bank 2 sensor reports too little oxygen in the exhaust, the computer reduces fuel on that side through negative trims, using a fast short-term correction and a slower, learned long-term one. P0175 sets when bank 2 trims have pulled out as much fuel as the computer allows and the exhaust still reads rich. The check runs whenever the engine is warm and in closed-loop fuel control, and the light usually comes on after two trips. Bank 2 is the side without cylinder 1, and its physical location depends on the engine. If P0172 is also set, both banks are rich and the cause is usually shared, such as airflow, fuel pressure or EVAP vapor. P0175 alone points toward something on the bank 2 side, like a leaking injector. ## What are the symptoms of P0175? - Check engine light on - Fuel smell from the exhaust - Black smoke on acceleration - Poor fuel economy - Rough idle ## What causes P0175? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Faulty or contaminated MAF sensor** (common). A MAF sensor that over-reports airflow makes the computer inject too much fuel on both banks, so P0172 usually sets alongside P0175. Contamination, an internal fault or an aftermarket intake that changes airflow across the sensor can cause it. Comparing MAF grams per second with the expected value, then cleaning the sensor, is a cheap first check. 2. **Leaking injector on bank 2** (common). A dripping or partly stuck-open injector on bank 2 floods one or more cylinders on that side, so only that bank runs rich. Deposits, wear and age are the usual causes. A misfire on a bank 2 cylinder, hard hot starts and a fuel smell can go with it. A shop can leak-test the rail or flow-test the injectors. 3. **High fuel pressure** (less common). A stuck fuel pressure regulator, a blocked return line or a faulty pressure control system raises pressure on the whole fuel rail, so both banks usually run rich. On regulators with a vacuum hose, fuel inside the hose means the diaphragm has failed. A fuel pressure gauge test against the factory spec confirms high pressure. 4. **Stuck-open purge valve** (less common). A purge valve that sticks open lets fuel vapor from the EVAP canister flow into the intake all the time instead of only when commanded. Because the vapor enters the shared intake, both banks usually go rich, especially at idle and right after refueling. Commanding the valve closed or pinching its hose while watching trims can confirm it. 5. **Biased bank 2 upstream oxygen sensor** (rare). A bank 2 upstream oxygen sensor that is contaminated or biased can report rich when the mixture is actually fine, so the computer keeps pulling fuel from that side. Oil burning or coolant leaks cause the contamination. Comparing its response with the bank 1 sensor, and checking for leaks and misfires, helps separate a sensor fault from real rich running. ## How do you diagnose P0175? 1. Compare fuel trims for bank 1 and bank 2; only bank 2 rich points to a cause on that side. 2. Check MAF readings and clean the sensor. 3. Test fuel pressure and look for a leaking regulator. 4. Close off the purge valve and watch trims; then leak-test bank 2 injectors. 5. Check the bank 2 oxygen sensor response with a propane or snap-throttle test. ## How do you fix P0175, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Clean or replace the MAF sensor | $15-$450 | When both banks are rich. | | Replace leaking bank 2 injectors | $300-$1,200 | Cost depends on access and injector type. | | Replace the upstream bank 2 oxygen sensor | $150-$400 | When it reads wrong compared with bank 1. | Full price breakdowns: [mass air flow sensor replacement cost](/cost/mass-air-flow-sensor-replacement), [oxygen sensor replacement cost](/cost/oxygen-sensor-replacement), [catalytic converter replacement cost](/cost/catalytic-converter-replacement). ## Is it safe to drive with P0175? > **Drive to a shop this week.** Short drives are usually OK, but rich running can overheat the catalytic converter and wash oil off cylinder walls. Stop driving if there is a strong raw fuel smell. ## Will P0175 fail an emissions test? P0175 keeps the check engine light on, which fails an OBD-II emissions test in most states. Rich running also raises carbon monoxide and hydrocarbons and can overheat the bank 2 catalytic converter, which may later set P0430. After the repair, clear the code and drive several days so fuel trims relearn and the monitors complete before testing. ## After the repair: clearing P0175 Clear the code or reset fuel trims after the repair, then compare bank 1 and bank 2 trims at warm idle and about 2,500 RPM. Bank 2 should no longer be strongly negative and should sit close to bank 1. The fuel smell should fade. Drive several mixed trips and recheck for pending codes to confirm the repair held. ## How to prevent P0175 - Do not top off the tank after the pump clicks off; it can harm the EVAP system. - Have a raw fuel smell or hard hot starting checked early for leaking injectors. - Clean or replace a contaminated MAF sensor before it pushes both banks rich. - Fix oil burning or coolant leaks that can contaminate the bank 2 oxygen sensor. - Change the oil after any long period of rich running to remove fuel dilution. ## Codes often seen with P0175 - [P0172](/codes/p0172): System Too Rich (Bank 1) - [P0174](/codes/p0174): System Too Lean (Bank 2) - [P0430](/codes/p0430): Catalyst System Efficiency Below Threshold (Bank 2) - [P0300](/codes/p0300): Random/Multiple Cylinder Misfire Detected ## Frequently asked questions ### Can I drive with P0175? Yes, for short distances. Rich running wastes fuel, fouls plugs and can damage the catalytic converter, so get it checked within a week or two. Stop driving if you smell strong raw fuel, see fuel dripping or the check engine light flashes, since those signs point to a fire risk or severe misfire. ### Why do P0172 and P0175 show up together? Both banks being rich means the cause is usually shared, such as the MAF sensor, high fuel pressure or a stuck-open EVAP purge valve. One bad injector would usually affect only one bank. Start with the shared parts, and look at bank 2 injectors only when P0175 shows up without P0172. ### Can a bad oxygen sensor cause P0175? It can, but less often than a fuel or airflow problem. A contaminated or biased bank 2 upstream sensor can report rich when the mixture is fine, so the computer wrongly pulls fuel from that bank. Check fuel trims, compare both banks' sensors and test its response before replacing it. ### How much does it cost to fix P0175? Most P0175 repairs cost $15-$1,200. Cleaning the MAF costs $15-$100, while a new MAF installed can reach $450. A bank 2 upstream oxygen sensor runs $150-$400, and replacing leaking bank 2 injectors is $300-$1,200 depending on access and injector type. Good diagnosis prevents paying for parts you do not need. ### Where is bank 2 on my engine? Bank 2 is the row of cylinders that does not include cylinder 1. On a V6 or V8 it may be the left, right, front or rear side depending on how the engine sits in the car. Service information for your engine shows which side it is and where its oxygen sensor is. ### Can I fix P0175 myself? Some of it. Reading and comparing fuel trims, cleaning the MAF sensor and checking the purge valve are reasonable home steps with a scan tool. Fuel pressure testing and injector replacement involve pressurized fuel and often removing the intake manifold on V engines, so a shop is usually the safer choice. ### Why does my exhaust smell like gas with P0175? A fuel smell from the exhaust is common with P0175. The extra fuel does not fully burn, so it leaves the tailpipe as hydrocarbons and sometimes black smoke. A strong smell of raw fuel around the engine, rather than from the exhaust, can mean a leak and should be checked right away. ### Can P0175 damage the catalytic converter? Yes, over time. Unburned fuel from bank 2 burns inside that bank's catalytic converter, overheating it and possibly melting or clogging its core. That can later set P0430. Fixing P0175 promptly is far cheaper than replacing a converter, one of the costliest emissions parts on a car. ### Can a four-cylinder engine set P0175? Usually not. Most four-cylinder engines have only one bank, so they set P0172 for a rich condition instead. P0175 appears on V6, V8 and flat engines, plus a few inline six-cylinder engines that use two upstream oxygen sensors. If you see P0175, your engine has a separate bank 2 fuel trim. ### Can bad spark plugs cause P0175? Not usually as a direct cause. A misfiring plug lets unburned oxygen into the exhaust, which tends to make the oxygen sensor read lean, not rich. However, long rich running fouls plugs, so you may need new plugs after fixing the real cause. Look for black, sooty deposits on them. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) ## Other fuel and air metering codes - [P0153 O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)](https://diagxcar.com/codes/p0153) - [P0155 O2 Sensor Heater Circuit (Bank 2 Sensor 1)](https://diagxcar.com/codes/p0155) - [P0156 O2 Sensor Circuit (Bank 2 Sensor 2)](https://diagxcar.com/codes/p0156) - [P0157 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)](https://diagxcar.com/codes/p0157) - [P0158 O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)](https://diagxcar.com/codes/p0158) - [P0161 O2 Sensor Heater Circuit (Bank 2 Sensor 2)](https://diagxcar.com/codes/p0161) - [P0171 System Too Lean (Bank 1)](https://diagxcar.com/codes/p0171) - [P0172 System Too Rich (Bank 1)](https://diagxcar.com/codes/p0172) - [P0174 System Too Lean (Bank 2)](https://diagxcar.com/codes/p0174) - [P0191 Fuel Rail Pressure Sensor "A" Circuit Range/Performance](https://diagxcar.com/codes/p0191) - [P0430 Catalyst System Efficiency Below Threshold (Bank 2)](https://diagxcar.com/codes/p0430) ## Symptoms - [Why is black smoke coming from my exhaust?](https://diagxcar.com/symptoms/black-smoke-from-exhaust) - [Why does my car smell like gas?](https://diagxcar.com/symptoms/car-smells-like-gas) - [Why does my car smell like rotten eggs?](https://diagxcar.com/symptoms/car-smells-like-rotten-eggs) ## Repair costs - [Mass air flow sensor replacement cost](https://diagxcar.com/cost/mass-air-flow-sensor-replacement): $150-$450 - [Oxygen sensor replacement cost](https://diagxcar.com/cost/oxygen-sensor-replacement): $150-$450 - [Catalytic converter replacement cost](https://diagxcar.com/cost/catalytic-converter-replacement): $1,000-$3,000 ## Terms explained - [What is Fuel trim?](https://diagxcar.com/glossary/fuel-trim) --- Source page: https://diagxcar.com/codes/p0175 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.