The BMW Diagnostic Trouble Code (DTC) P0700 corresponds to a "Transmission Control System (MIL Request)" condition. Here's what it typically means:
**P0700 - Transmission Control System (MIL Request)**
This DTC is a generic code that indicates that the transmission control module (TCM) has detected a malfunction within the transmission control system. When the TCM identifies an issue, it can request the illumination of the Malfunction Indicator Lamp (MIL), also known as the Check Engine Light, to alert the driver to a potential problem.
While P0700 itself does not provide specific information about the nature of the transmission issue, it serves as a signal that further diagnostic codes (sub-codes) are likely stored in the TCM. These sub-codes will provide more detailed information about the specific transmission problem.
Common causes of a P0700 code in a BMW include:
1. **Faulty Sensors:** Malfunctioning sensors related to the transmission, such as the vehicle speed sensor, transmission range sensor, or other input sensors, can trigger this code.
2. **Wiring or Connector Issues:** Damaged or corroded wiring, connectors, or terminals within the transmission control system can result in communication errors.
3. **TCM Malfunction:** A fault within the transmission control module itself can lead to this code.
To diagnose and address a P0700 code, a qualified technician typically performs the following steps:
1. **Retrieve Sub-Codes:** Use a diagnostic scan tool capable of accessing the TCM to retrieve sub-codes that provide more specific information about the transmission issue.
2. **Visual Inspection:** Inspect the wiring, connectors, and terminals related to the transmission control system for damage, corrosion, or loose connections.
3. **Sensor Testing:** Test the sensors within the transmission control system, including the vehicle speed sensor and transmission range sensor, to ensure they are functioning correctly.
4. **TCM Testing:** Evaluate the operation of the transmission control module to check for internal faults.
5. **Data Monitoring:** Use a diagnostic scan tool to monitor live data from the transmission system to help identify any discrepancies or abnormalities.