The BMW Diagnostic Trouble Code (DTC) P1129 corresponds to a "Long Term Fuel Trim Multiplicative Air System Too Rich" condition. Here's what it typically means:
**P1129 - Long Term Fuel Trim Multiplicative Air System Too Rich**
This DTC indicates that the engine control module (ECM) has detected a long-term fuel trim (LTFT) condition where the air-fuel mixture is too rich in the multiplicative air system. In simpler terms, it means that the engine is running with too much fuel and not enough air.
Common causes of a P1129 code in a BMW include:
1. **Fuel Delivery Issues:** Problems with the fuel delivery system, such as a leaking fuel injector, high fuel pressure, or excessive fuel flow, can result in a rich air-fuel mixture.
2. **Faulty Mass Airflow Sensor (MAF):** The MAF sensor measures the amount of air entering the engine, and a malfunctioning MAF sensor can provide incorrect data to the ECM, leading to a rich condition.
3. **Faulty Oxygen Sensors:** Oxygen sensors play a crucial role in adjusting the air-fuel mixture. Malfunctioning oxygen sensors can provide inaccurate data to the ECM.
4. **Exhaust Restrictions:** A restricted or partially blocked exhaust system can disrupt the exhaust flow, affecting the air-fuel mixture.
To diagnose and address a P1129 code, a qualified technician typically performs the following steps:
1. **Visual Inspection:** Inspect the fuel delivery system, including the fuel injectors and fuel pressure regulator, for leaks or issues.
2. **Check Mass Airflow Sensor:** Test the mass airflow sensor for proper function and clean it if necessary.
3. **Inspect Oxygen Sensors:** Test the operation of the oxygen sensors to ensure they are functioning correctly.
4. **Exhaust Inspection:** Check for exhaust restrictions or blockages that may be affecting the air-fuel mixture.
5. **Data Monitoring:** Use a diagnostic scan tool to monitor live data, including sensor readings, to help identify the source of the rich condition.
