Error P0175 – how to fix?

Code definition P0175

P0175 System Too Rich (Bank 2)

What does the code P0175 mean

P0175 indicates the engine control module (ECM) detects too much fuel and too little oxygen in the fuel-air ratio (AFR). This code is set when the ECM cannot compensate for the amount of air or fuel required to bring the air-to-fuel ratio back to set parameters.

For gasoline engines, the most efficient and economical air-fuel ratio is 14.7: 1, or 14.7 parts air to 1 part fuel. This ratio also ensures maximum power during the combustion process.

The combustion process is very simple but gentle. Most vehicles have four to eight combustion chambers in an engine. Air, gasoline, and a spark enter the combustion chambers to create an “explosion” (better known as combustion). A spark appears in each combustion chamber a nanosecond after air and fuel reach the chamber to ignite it. There is a piston in each combustion chamber; each piston is pushed down by combustion at a rapid rate and at different times.

The timing difference of each piston is determined by the air-fuel ratio and the engine timing. After lowering the piston, it must return to the upper position in order to be in time for the next combustion process. The piston is forced to return to the top slowly each time one of the remaining cylinders undergoes its own combustion process as they are all connected to a rotating assembly known as the crankshaft. It’s almost like a juggling effect; at any given moment, one piston rises while another is at the top and another is descending.

If anything in this process is omitted, the internal engine components will either work harder and work against each other, or the engine may not work at all. For P0175, increased fuel economy is likely because the ECM has detected that too much fuel is being used.

What causes the code P0175?

• Clogged, choked, or leaking fuel injector.
• Faulty fuel regulator
• Faulty or dirty mass air sensor
• Coolant temperature sensor defective
• Defective thermostat
• The ECM must be reprogrammed
• Damaged or dirty oxygen sensor
• Vacuum leak
• Fuel supply problem
• Incorrect fuel pressure

What are the symptoms of the P0175 code?

• Increased fuel consumption
• Soot or black sludge in the exhaust gas
• Engine headlight illumination
• Strong exhaust odors

How does the mechanic diagnose the P0175 code?

• Check the fuel pressure
• Checks fuel injectors for restrictions
• Checks fuel injector pulse
• Checks fuel lines for lumps or cracks.
• Checks all vacuum lines for cracks and damage
• Checks the oxygen sensors
• It uses a scan tool to read the engine temperature and then compares the results with an infrared thermometer

The most common errors when diagnosing the P0175 code

• Not checking the engine temperature with a scan tool and comparing it with a thermometer
• Belief that a component is defective without testing it.

How serious is the P0175 code?

• A system that works too richly will force the catalytic converter to filter more contaminants, reducing its lifetime.
• The resulting increase in fuel consumption can be very costly.
• Inadequate air-fuel ratio causes the engine to work harder, which shortens its life
• The engine will generate higher levels of harmful pollutants.

What repairs can fix the code P0175?

1. Replace cracked or damaged vacuum lines
2. Clean or replace oxygen sensors
3. Clean or replace the mass air flow meter
4. ECM reprogramming
5. Replacing the fuel pump
6. Replacing the fuel filter
7. Replace a damaged or punctured fuel line
8. Replace a damaged fuel injector
9. Replacing a clogged thermostat
10. Replacing a damaged coolant temperature sensor

Additional notes regarding code P0175

I strongly recommend that you check that your vehicle’s cooling system is working properly. If the vehicle is running in excessively cold conditions, the engine will always run rich. This is because the ECM is designed to run at a rich rate in cold weather to help warm up the engine faster. If the coolant temperature sensor is broken or the thermostat is open, the vehicle may never reach warm temperature, resulting in it always running rich.