Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0175: System too rich (Bank 2)

The ECU is subtracting fuel but Bank 2 still appears too rich.

What P0175 means

The ECU is subtracting fuel but Bank 2 still appears too rich. This code generally applies only to engines with a second cylinder bank. It describes the mixture correction limit and does not automatically condemn the Bank 2 lambda sensor.

Can I still drive?

Arrange repair soon. With a steady warning light and completely normal running, restrict driving to a short, gentle journey for diagnosis. Stop and arrange recovery if the light flashes, the engine misfires or shakes, the car stalls or loses substantial power, black smoke is heavy, or raw fuel can be smelt strongly or seen leaking.

Symptoms

  • Engine-management light, sometimes without another obvious symptom.
  • Rough idle, poor acceleration or misfire.
  • Difficult starting and increased fuel consumption.
  • Fuel-smelling or dark exhaust.

Common causes

  • Leaking or incorrectly controlled Bank 2 injector.
  • Excessive fuel pressure or defective pressure regulation.
  • Contaminated or inaccurate MAF/MAP sensor, particularly if both banks are rich.
  • Restricted air intake or badly clogged filter.
  • Incorrect coolant- or air-temperature input.
  • EVAP purge fault introducing excessive fuel vapour.
  • Bank 2 upstream lambda sensor, connector or wiring fault.
  • Less commonly, exhaust restriction, mechanical trouble or ECU/wiring fault.

Safe first checks

  • Record every code and freeze-frame value. If P0172 is present too, shared causes deserve attention; if only P0175 is present, Bank 2-specific wiring, injector, exhaust and sensor checks become more relevant. With the engine cold and off, inspect the air filter and intake path, accessible connectors and visible Bank 2 wiring. Check for a rising oil level or strong fuel smell in the oil. If familiar with scan data, compare both banks’ fuel trims rather than assuming the sensor is faulty. Do not loosen fuel lines or attempt pressure tests without the correct equipment.

Typical UK fix cost

Approximately £40–£100 for diagnosis and £100–£350 fitted for many straightforward confirmed faults. A minor intake or connector repair may be lower; multiple/direct injectors, pressure-control work or catalytic-converter damage can exceed £500. Treat these figures as planning allowances only.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

Sources

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.