BMW Diagnostic Trouble Code P1191 - BMW - Pre-Catalyst Fuel Trim System Bank 2

Code Definition: P1191 - Pre-Catalyst Fuel Trim System Bank 2

The P1191 code is a generic trouble code that indicates a problem with the pre-catalyst fuel trim system in bank 2. The pre-catalyst fuel trim system is responsible for ensuring that the proper amount of fuel is delivered to the engine before it enters the catalytic converter. When the fuel trim system malfunctions, it can cause problems with the engine's performance and emissions.

Possible Causes:

• Faulty fuel injectors
• Clogged or dirty fuel filters
• Malfunctioning fuel pressure regulator
• Faulty engine coolant temperature sensor
• Faulty intake air temperature sensor
• Faulty manifold absolute pressure sensor
• Low fuel pressure
• High fuel consumption

Symptoms:

• Illuminated check engine light
• Poor engine performance
• Rough idling
• Misfire or pinging noise from the engine
• Decreased fuel efficiency
• Difficulty starting the engine

Diagnostic Procedure:

1. Use a scan tool to retrieve the trouble code and view the freeze frame data to determine when the code was set and under what operating conditions.
2. Inspect the fuel system for any signs of leaks, blockages, or other issues.
3. Check the fuel injectors and replace them if necessary.
4. Check the fuel filters and replace them if necessary.
5. Test the fuel pressure regulator and replace it if necessary.
6. Check the engine coolant temperature sensor and replace it if necessary.
7. Check the intake air temperature sensor and replace it if necessary.
8. Check the manifold absolute pressure sensor and replace it if necessary.
9. Check the fuel pressure and adjust it if necessary.
10. Perform a road test to see if the condition persists. If the code does not return, the problem may have been intermittent or related to a loose connection.
11. If the code returns, consider replacing additional components such as the fuel pump or fuel rail.

Repair Information:

1. Replace the faulty fuel injectors.
2. Replace the clogged or dirty fuel filters.
3. Replace the malfunctioning fuel pressure regulator.
4. Replace the faulty engine coolant temperature sensor.
5. Replace the faulty intake air temperature sensor.
6. Replace the faulty manifold absolute pressure sensor.
7. Adjust the fuel pressure to the recommended specifications.
8. Clear the code and perform a road test to verify the repair.

It's important to note that this is a general guide and the exact repair procedure may vary depending on the year, make, and model of your BMW. Always consult a professional mechanic if you're unsure about how to diagnose or repair an issue with your vehicle.************************ **************