The Bmw 801c20 fault code indicates that the vehicle’s Central Fault Memory (CFM) is full. This can be a perplexing issue, especially when the car seems to be operating perfectly fine. This article explores the 801C20 code, its potential causes, and troubleshooting steps.
What is BMW Fault Code 801C20?
The 801C20 code specifically signifies that the CFM, responsible for storing diagnostic trouble codes (DTCs) from various modules within the BMW, has reached its storage capacity. While the car might drive normally, a full CFM can prevent the system from logging new, potentially more serious, faults.
Potential Causes of 801C20
A full CFM often results from an accumulation of minor, unresolved faults. These could include:
- Intermittent Issues: Temporary malfunctions that trigger a fault code but don’t persist.
- Sensor Glitches: Occasional erroneous readings from sensors that are otherwise functional.
- Communication Errors: Brief interruptions in communication between modules.
- Low Battery Voltage: A weak battery can cause various system malfunctions and trigger multiple fault codes. Although a battery replacement might seem like a solution, the underlying faults that occurred during the low voltage period will remain logged.
Troubleshooting BMW 801C20
Addressing the 801C20 code requires clearing the CFM. Here are some steps to take:
- Using a Diagnostic Scanner: A BMW-compatible diagnostic scanner, such as the LAUNCH Creader Elite, can be used to read and clear fault codes. Specifically, accessing the ZGM (Central Gateway Module) is crucial as it manages the CFM. Clearing the memory in the ZGM should erase the 801C20 code.
- ZGM Module Reset: As suggested by some experienced BMW owners, resetting the ZGM module can effectively clear the entire fault memory. However, it’s important to note that this might temporarily trigger other error codes as modules re-initialize. These should clear themselves shortly after the reset. Using a diagnostic scanner to subsequently clear any remaining codes is recommended.
- Addressing Underlying Issues: Simply clearing the CFM without investigating the root causes of the logged faults is not a long-term solution. A thorough diagnostic scan of all modules should be performed to identify and rectify any underlying problems. This can prevent the CFM from filling up again.
Conclusion: Maintaining a Healthy CFM
While the BMW 801C20 fault code might not immediately impact drivability, it’s crucial to address it promptly. A full CFM hinders the diagnostic system’s ability to log new faults, potentially masking serious problems. Utilizing a diagnostic scanner to clear the memory and investigate the root causes of the stored codes is essential for maintaining the health and reliability of your BMW. Regularly clearing minor, intermittent faults can prevent the CFM from becoming full and ensure the proper functioning of the diagnostic system.
