P0175 Code: Fuel Trim System Rich, Bank 2 (Chevrolet Guide)

P0175 on a Chevrolet is "Fuel Trim System Rich, Bank 2." The engine computer has been pulling fuel out of bank 2 for so long that it has hit its correction limit — something is adding fuel or removing air on that side. GM's service information is unusually blunt about the part most people replace first: an oxygen sensor will not cause this code without also setting its own circuit codes. Do not replace an oxygen sensor to address it. On late-model Silverados and Tahoes, GM has also documented a cause many shops never check: fuel getting into the crankcase oil and being pulled back into the engine through the PCV system.

What Does P0175 Mean?

Your engine computer (ECM) constantly adjusts fuel delivery using the front oxygen sensor on each bank. Fast adjustments are short-term fuel trim; the learned correction it carries forward is long-term fuel trim. Negative numbers mean the ECM is removing fuel because it sees a rich mixture.

P0175 sets when bank 2's long-term trim has stayed at its rich-correction limit — the ECM is taking out as much fuel as it is allowed to and the mixture is still rich. GM's service information for its V6 family says the code sets when the weighted average of long-term trim is beyond a calibrated value for about three minutes in closed loop. It is a Type B code.

GM also builds in a check. On many engines, when trim looks rich the ECM intrusively shuts off EVAP purge and re-tests, so it can tell whether fuel vapor from the charcoal canister was the cause. A P0175 that survives that test points at the engine itself.

GM's guidance on what normal looks like: short- and long-term trims within about ±10% is typical, and the system test passes within roughly −20% to +20%.

Where Bank 2 Is

Only engines with two banks can set P0175. On a four-cylinder Cruze, Malibu, Equinox or Trax, the equivalent rich code is P0172.

• V8 Silverado, Tahoe, Suburban, Camaro, Corvette: cylinder 1 is on the driver's side, so bank 2 is the passenger side (cylinders 2-4-6-8).
• 3.6L V6: GM numbers the right bank (cylinders 1-3-5) viewed from the flywheel end as bank 1, so bank 2 holds cylinders 2-4-6. In a transverse installation (Traverse, Equinox V6, Impala) bank 2 is the bank nearer the radiator. In a longitudinal installation (Camaro, Colorado) it is the driver's side.
• 4.3L V6 trucks: same convention as the V8s.

P0175 Alone vs With P0172

This is the most useful diagnostic fork, and it costs nothing to apply.

A single-bank rich condition is hard to produce with a shared component like the MAF sensor or fuel pump, because both banks see the same air and the same pressure. When both banks are rich, start with the shared systems.

Fuel in the Oil

Here is the cause GM has documented repeatedly on late-model Chevrolets and that generic advice almost never mentions: raw fuel in the crankcase oil. The PCV system draws crankcase vapor into the intake, and if that vapor is rich with gasoline, both banks run rich.

GM bulletin 20-NA-200 ("Diagnostic Tip for MIL Illuminated – DTC P0172 and/or P0175 Set") covers 2014–2018 Silverado and Sierra with the 4.3L, 5.3L and 6.2L, 2015–2019 Tahoe and Suburban 5.3L, and Camaro and Corvette V8s. GM's concern is a high-pressure fuel pump leaking fuel into the crankcase. The test: disconnect the dirty-air side of the PCV system, plug the vacuum supply, and watch closed-loop fuel trims. If they return to normal, the high-pressure pump is the likely source. GM notes an oil change may not reveal it. (We read this bulletin through a republished copy rather than the NHTSA original.)

GM's PIP5647 covers a related but different case on the 2019 Silverado 1500 5.3L and 6.2L (and several small turbo engines): fuel trims around −20% on both banks, oil level overfull and smelling of fuel, caused by short trips or lot driving where the engine never gets hot enough to boil the fuel out of the oil. GM's fix is change the oil and filter and re-check the trims — and the bulletin says plainly: do not replace the fuel pump for this condition.

So before any parts: pull the dipstick. If the oil is over the full mark and smells of gasoline, you have found your direction.

The Injector Flow-Class Trap

GM bulletin 20-NA-098 covers 2014–2020 GM V6 and V8 gas engines, including the 5.3L L83/L84, 6.2L L86/L87 and LT1. GM's direct-injection injectors are built in flow classes, and installing the wrong class after a repair skews fuel trims and can set P0175, among others.

GM's instruction is to order replacement injectors by VIN using the eight-digit number on the injector body, which maps to a specific service part. If you are unsure, order the nominal-flow injector for every position being replaced.

That matters if your P0175 appeared after injector work. A bank 2 rich code on a truck that just had one or two injectors replaced is a strong hint that the flow class is wrong.

Symptoms of P0175

• Check engine light on
• Fuel smell, sometimes from the exhaust, sometimes from the oil
• Oil level over the full mark and smelling of gasoline (PCV/crankcase fuel causes)
• Poorer fuel economy
• Rough idle or misfire on a severely rich bank
• Black soot at the tailpipe
• P0172 alongside when the cause is shared

Causes and How to Confirm Each

How Is P0175 Diagnosed?

1. Record all codes and freeze-frame data. Fix misfire, injector, MAF, MAP and EVAP codes first — GM blocks P0175 from running while those are set.
2. Note whether P0172 is also set. One bank or both is your first fork.
3. Check the oil for overfill and fuel smell.
4. Watch live fuel trims at idle and steady cruise for both banks.
5. Command EVAP purge off and see whether the trims recover.
6. Do GM's PCV disconnect test on 2014–2019 V8 trucks (20-NA-200).
7. Check fuel pressure desired vs actual.
8. Run an injector balance test, and if injectors were recently replaced, check their body numbers against the correct service part.
9. Unplug the MAF and watch trims per GM's check.
10. Clear codes and drive long enough for the fuel trim monitor to complete — it needs several minutes of closed-loop operation.

Parts and Cost

GM Documents That Name P0175

Have a dealer check your VIN against current bulletins rather than relying on any article, including this one.

What Other P0175 Pages Get Wrong

• "P0175 means a bad O2 sensor." GM's service information says an O2 sensor will not cause this code without its own circuit codes, and tells technicians not to replace one for it.
• Putting bank 2 on the driver's side of a Silverado. On GM V8s, bank 2 is the passenger side.
• Listing P0175 for four-cylinder Chevys. A Cruze or Equinox four-cylinder sets P0172, not P0175.
• Replacing the fuel pump for fuel in the oil. GM's PIP5647 says not to for short-trip dilution. An oil change and re-check comes first.
• Citing a diesel bulletin for a gas truck. GM's 22-NA-128 involves P0172 on the 3.0L Duramax, not the 5.3L.
• Blaming the EVAP purge coverage. GM's purge valve special coverages list lean codes (P0171/P0174), not P0175.

Frequently Asked Questions

Is P0175 serious?

Not usually immediate, but a sustained rich mixture washes oil off cylinder walls, dilutes the oil and can overheat the catalytic converter over time. Fix it rather than living with it.

Which side is bank 2 on a Silverado?

The passenger side. Cylinder 1 is at the front of the driver's side on GM V8s, so bank 1 is the driver's side and bank 2 is the passenger side.

Can a bad O2 sensor cause P0175?

According to GM's own service information, not without also setting oxygen sensor circuit codes. If only P0175 is stored, look for a genuine rich condition rather than replacing the sensor.

Why does my oil smell like gas and I have P0175?

Fuel is getting into the crankcase — from short trips that never fully warm the engine (PIP5647) or, on 2014–2019 V8 trucks, possibly from a leaking high-pressure fuel pump (20-NA-200). The PCV system then feeds that fuel back into the engine and the trims go rich.

Will an oil change fix P0175?

If short-trip fuel dilution is the cause, GM's documented first step is exactly that: change the oil and filter, then re-check fuel trims. If they stay rich, keep diagnosing — the high-pressure pump and injectors are next.

Can a dirty air filter cause P0175?

A badly restricted air intake is listed in GM's diagnostic aids, and it is free to check. It is usually a shared cause, so expect P0172 alongside.