801C15

801C15 — Central Gateway Module (ZGM): Stored Fault Without Description ## What the Code Means

801C15 is an entry in the memory of the Central Gateway Module (ZGM), the central gateway for the vehicle network. In the short test printout the code appears without explanatory text — only the note “Fault is stored.” The source gives no description, no trigger conditions, and no link to a specific component.

The code was read from a BMW X3 F25 35i using a BT cable. It shows up in the same list as other entries from the same module: 801C06 (also “Fault is stored”) and 801C20 (“ZGM: central fault memory full — no control-module fault”). At the same time, other modules logged undervoltage codes: 213A21 “Vehicle voltage: Voltage too low,” 802102 (JBE: undervoltage), 48279B (ICM: Undervoltage in vehicle), 8029D4 (SMFA: Undervoltage detected), 801A4C (SINE: undervoltage detected in internal voltage supply), plus CD9437 (DSC/FlexRay: Communications fault) and E1C440 (stored but not current).

The thread consensus is a discharged or worn battery as the cause of this code set, not a failure of the ZGM itself: during voltage sags the modules log communication and internal voltage errors, and the central gateway stores them in shared memory. In this context, 801C15 is a consequence of overall low vehicle voltage, not a standalone gateway fault. ## Symptoms

The symptoms below apply to the vehicle as a whole and are not attributed directly to code 801C15 in the source.

• One-time no-start: all electrics came on but the starter motor didn't engage; after a jump start the engine fired immediately.
• Battery voltage drop to 8.4 V during cranking (per the hidden menu), then rising to 14.0 V at idle — the alternator is working.
• Resting voltage: 12.4 V right after a full charge, 12.1 V after 12 hours parked, 12.2 V in the hidden menu before startup.
• No warning lights, no low-battery indicator, no flickering lights.
• The JBE, ICM, SMFA, and SINE modules all logged undervoltage codes at the same time, along with code CD9437 (DSC/FlexRay: Communications fault).
• Autozone test: alternator and battery passed, starter motor showed an error; the owner's own scan found no starter motor codes. ## Diagnosis and Repair

1. Check the battery's condition and build date. The thread notes that at 4+ years old the battery should be treated as a consumable and replaced preventively.
2. Fully charge the battery (the thread starter used a trickle charger, later a CTEK, including connecting under the hood) and check resting voltage afterward.
3. Verify the installed battery specs: BMW 12V 90Ah 900A, 160 RC, 900CCA, part number 158 558-10 US (158558.0).
4. After installing a new battery, register it in the vehicle — the modules misreport battery condition without registration.
5. Treat the cluster of varied codes, including 801C15, as a consequence of low voltage, not as separate module failures.
6. Once the power issue is fixed, run another short test and clear the fault memory.

Symptoms

The symptoms below apply to the vehicle as a whole and are not attributed directly to code 801C15 in the source.

• One-time no-start: all electrics came on but the starter motor didn't engage; after a jump start the engine fired immediately.
• Battery voltage drop to 8.4 V during cranking (per the hidden menu), then rising to 14.0 V at idle — the alternator is working.
• Resting voltage: 12.4 V right after a full charge, 12.1 V after 12 hours parked, 12.2 V in the hidden menu before startup.
• No warning lights, no low-battery indicator, no flickering lights.
• The JBE, ICM, SMFA, and SINE modules all logged undervoltage codes at the same time, along with code CD9437 (DSC/FlexRay: Communications fault).
• Autozone test: alternator and battery passed, starter motor showed an error; the owner's own scan found no starter motor codes.

Diagnosis and Repair

1. Check the battery's condition and build date. The thread notes that at 4+ years old the battery should be treated as a consumable and replaced preventively.
2. Fully charge the battery (the thread starter used a trickle charger, later a CTEK, including connecting under the hood) and check resting voltage afterward.
3. Verify the installed battery specs: BMW 12V 90Ah 900A, 160 RC, 900CCA, part number 158 558-10 US.
4. After installing a new battery, register it in the vehicle — the modules misreport battery condition without registration.
5. Treat the cluster of varied codes, including 801C15, as a consequence of low voltage, not as separate module failures.
6. Once the power issue is fixed, run another short test and clear the fault memory.