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BMW 801C20: central fault memory full
Not a broken part. The central gateway's fault log is full and can't store new entries. Fix whatever is filling it, then clear it with a BMW-capable tool.
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Codes on this page
| Code | Definition | Source |
|---|---|---|
| 801C20 | Central gateway module (ZGM): central fault memory full | Bimmerfest owner thread |
P-codes are the generic OBD-II codes any reader shows. Six-character and four-character hex codes are BMW's own, read with a BMW-capable scanner; the wording is BMW's, from the source shown.
What it means
On the F01 7 Series and later BMWs, the central gateway module (ZGM) keeps a central log of faults and Check Control messages from all the modules. BMW's training material says it holds between 250 and 1,000 entries; when it is full no new faults or messages are stored, and the log can only be cleared with the BMW diagnostic system. Each fault is logged at most ten times so that one constant fault can't fill it.
Can I keep driving?
Yes. 801C20 itself doesn't affect driving. The faults that filled the log might, so read all modules.
Usual causes on BMWs
| Cause | Cars most affected | What you notice | Evidence |
|---|---|---|---|
| Many stored faults from other modules | F-series and later | Owners report other faults (for example lighting shorts) that need fixing first, then clearing all faults with ISTA. | Owner report |
| Low battery voltage or a parasitic drain | All | Low voltage makes many modules log faults at once. | — |
A bulletin isn't a recall and doesn't mean your car has the problem; open it for the exact models and build dates.
What to do
- Read every module, not just the engine.
- Fix active faults, then clear the central fault memory with a BMW-capable tool.
- If it fills again quickly, check the battery and charging system.
Warnings it can bring up
Sources
- BMW technical training: F01 System Functions (central fault memory in the ZGM), hosted on Bimmerfest
- Bimmerfest owner thread: Central Gateway Module 801C20 "Central fault memory full"
- NHTSA: BMW technical service bulletins and recalls by VIN
Bulletins are cited in the tables above. Explanations are ours; where a source is an owner report rather than BMW, it is labelled as one.