P0175 System Too Rich Bank 2

With closed-loop control the engine module corrects the injected fuel using the oxygen sensor: short-term fuel trim reacts within fractions of a second, long-term trim stores a learned base correction per load and speed range. Positive values mean fuel is being added because the mixture was lean, negative values mean fuel is being removed; around ±10 % is normal. P0175 is the bank 2 counterpart of P0172: long-term trim at its lower limit, mixture still rich. GM evaluates it like bank 1 with a passive test before the first purge and an active test with the purge valve closed; Ford at −25 % with purge off. Two trips, no limp mode. P0175 alone points to a bank-specific cause such as a leaking injector on bank 2; together with P0172 to fuel pressure, purge, ethanol learning on flex-fuel vehicles or fuel in the oil. GM and Ford bulletins document wrongly learned ethanol content and a purge valve stuck open as causes.

Likely causes

Symptoms

• Check engine light on (after two drive cycles)
• Higher consumption, fuel smell
• Black smoke, sooted spark plugs
• Rough idle or starting problems after refuelling; converter damage possible later

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

1. Compare trims on both banks
2. Check fuel pressure
3. Test injectors

Parts involved

Related codes

References: law.cornell.edu, gsi.ext.gm.com, fordservicecontent.com, saabwisonline.com.