P0175: System Too Rich (Bank 2)

What is P0175?

The P0175 code shows up when the Engine Control Module (ECM) or Powertrain Control Module (PCM) detects too much fuel or insufficient oxygen in the air fuel ratio.

Your car needs the correct air fuel ratio and spark (via spark plugs) for the perfect level of combustion to run your vehicle. And for a smooth ride, the fuel and oxygen levels need to change as you speed, slow down or rev up your engine.

How does this work?

The ECM or PCM sets the required air fuel ratio using the information sent by the mass airflow sensor (MAF sensor), crankshaft position sensor, and engine coolant temperature sensor according to your car’s engine speed.

The PCM then uses readings from the heated oxygen sensor (O2 sensor) to further adjust the air fuel ratio based on oxygen levels in the exhaust gas.

Ideally, your vehicle’s air fuel ratio should be 14:7:1, or 14:7 parts air and 1 part fuel.

But sometimes, the Engine Control Module or Powertrain Control Module may be unable to balance the air fuel ratio due to factors like a vacuum leak, faulty fuel injector, or fuel delivery issues.

If the imbalance causes a rich condition (excess fuel and insufficient oxygen,) the ECM registers a code P0175.

Common symptoms

An imbalanced air fuel mixture may turn on your Check Engine Light and cause serious engine and fuel economy problems — affecting your car’s performance.

Here are some more signs of a DTC P0175:

• Increased fuel consumption: Fuel consumption increases when your vehicle exhausts unburnt fuel from your tailpipe. A faulty fuel injector could also inject more fuel, leading to high fuel consumption. 
• Black residue from exhaust: You may find soot or black residue in your exhaust, usually due to unburnt fuel in the system. 
• Strong exhaust odors: A vehicle with a P0175 code will have strong gasoline or diesel odor that smells like rotten eggs. This can also indicate a possible exhaust leak. 
• Rough idle: Improper combustion or unburnt fuel causes your car to idle roughly or misfire.

Can I still drive?

Symptoms like rough idle or misfiring may probably allow you to drive with code P0175 for some time. But if neglected, code P0175 can become very severe, leading to expensive repairs.

For example, if the fuel system runs too rich, your car may force the catalytic converter to filter out more pollutants, shortening its lifespan. Or, an improper air fuel mixture may overwork the engine causing serious engine damage.

So it’s best to call the nearest auto repair shop to resolve the Check Engine Light and get your car fixed to avoid expensive repairs and additional replacement costs.

P0175 causes

DTC P0175 can be caused by anything from a faulty fuel pressure sensor, or a catalytic converter to a MAF sensor malfunction.

Some common causes include:

• A clogged, stuck, or leaking fuel injector: This results in the fuel injector pushing extra fuel into the system. Leaks in the fuel system may also make it seem like the injector isn’t doing its job. 
• Faulty fuel regulator: A faulty fuel pressure regulator means it’ll incorrectly supply excess fuel to the fuel injector. 
• Dirty mass airflow sensor: A dirty mass air flow sensor restricts air flow and intake of oxygen, resulting in a rich condition. 
• Bad thermostat: This results in a rich fuel trim value as a bad thermostat can’t maintain the optimal engine temperature. 
• Dirty or faulty oxygen sensor: An issue with the O2 sensor or AF sensor means it’ll send inaccurate oxygen readings to the ECM, prompting the fuel injector to send more fuel. 
• Vacuum leak: A vacuum leak lets unmonitored oxygen escape before mixing with the fuel, causing an imbalanced air fuel mixture.

Other causes may also be:

• A damaged fuel pump check valve
• Incorrect fuel pressure
• A worn-out spark plugs
• A dirty air filter
• Fuel delivery issues

Diagnosis

If you misdiagnose the error code P0175, you may replace the wrong parts to resolve the code. So it’s best to contact a professional repair shop when you spot an issue.

Your mechanic may do the following checks to diagnose the P0175 trouble code:

• They may start by inspecting the fuel pressure.
• Your mechanic may then check if the fuel injector is blocked.
• Next, they’ll examine the fuel injector pulse.
• The mechanic will then check the vacuum lines for any damage or cracks.
• They may also check if the oxygen sensor is working properly.
• Finally, your mechanic may use a scan tool to read and compare the engine temperature to an infrared thermometer reading.

There’s a high possibility of misdiagnosis if the mechanic doesn’t compare the engine temperature to the thermometer. Or if they assume a component to be defective without proper testing.

Typically, analyzing fuel trim values and the freeze frame data with a scan tool should help with diagnosing the issue correctly.

Possible repairs for P0175 & Costs

Depending on the cause and diagnosis of the code P0175, your mechanic may repair or replace the following:

• Cracked or leaking vacuum lines
• Oxygen sensor or the AF sensor (AFR sensor)
• Mass air flow sensor
• Fuel pump
• Fuel filter 
• Fuel Injector
• Thermostat
• EGR valve
• Coolant temperature sensor
• Spark plugs

Repair cost:

Here are the estimated costs of some components or repairs:

• Vacuum leak: $100 – $200 
• Replacing MAF sensor: $300 
• Cleaning MAF sensor: $100 
• Fuel pressure regulator: $200 – $400 
• Fuel pump : $1300 – $1700 
• Fuel filter: $79 – $86
• Exhaust repair: $100 – $200 
• EGR valve: $370 – $500
• Air-fuel sensor (AFR sensor)/Oxygen sensor: $200 – $300

The replacement costs depend on which part requires repair or replacing, the vehicle’s make, location, and local labor charges.