Complete guide to Sensotronic Brake Control diagnostic trouble codes
Diagnostic Reference
The SBC (Sensotronic Brake Control) system by Bosch monitors braking operations, pump RPM, and fluid service intervals. When faults are detected or thresholds exceeded, it logs diagnostic trouble codes and may display "Service brake! Visit workshop!" on your dashboard.
| Code | Description | Severity |
|---|---|---|
| C249F | Check operating time of component A7/3 (SBC hydraulic unit) — The lifetime counter (~300,000 brake actuations) has run out. Triggers "Service brake! Visit workshop!". C249F guide | Medium |
| C2498 | Service threshold reached — The SBC unit's own wear monitoring has hit its service limit. Often logged with C249F. C2498 guide | Medium |
| C235A | Service threshold reached — Same wear-monitoring family as C2498. C235A/C235C guide | Medium |
| C235C | Service threshold reached — Same family: a different monitored counter, same meaning. Not a relay fault. | Medium |
| C235E | Service threshold reached — Same family. | Medium |
| C2359 | Service threshold reached — Same family. | Medium |
| C235D | Check operating time of component A7/3 (SBC hydraulic unit) — Same wording as C249F: operating-time limit reached. | Medium |
| C2131 | Pressure reservoir faulty — The pressure accumulator inside the hydraulic unit has failed. Rebuild or exchange required. | High |
| C2132 | Pressure reservoir: check pretension pressure — Accumulator pre-charge pressure out of specification. | High |
| C25D4 | Hydraulic fault: no or insufficient pressure supply — The unit can't supply working pressure. | High |
| C26BB | Hydraulic fault: malfunction in pressure supply — Pressure supply fault in the hydraulic unit. | High |
| C26BE | Hydraulic fault: malfunction in pressure supply — Pressure supply fault in the hydraulic unit. | High |
| C223C | Hydraulic fault: pressure regulator, left front wheel — Internal hydraulic fault on the left-front circuit. | High |
| C223D | Hydraulic fault: pressure regulator, left front wheel — Internal hydraulic fault on the left-front circuit. | High |
| C22BD | Hydraulic fault: pressure regulator, right front wheel — Internal hydraulic fault on the right-front circuit. | High |
| C233D | Hydraulic fault: pressure regulator, left rear wheel — Internal hydraulic fault on the left-rear circuit. | High |
| C23BD | Hydraulic fault: pressure regulator, right rear wheel — Internal hydraulic fault on the right-rear circuit. | High |
| C217B | Check power supply of component valve relay — Check supply and wiring to the SBC unit first. It can also be internal. | Medium |
| C226F | Control unit A7/3n1 (SBC control unit), internal fault — The electronics inside the SBC unit have failed. | High |
| C22EF | Control unit A7/3n1 (SBC control unit), internal fault — As C226F. | High |
| C254F | Control unit A7/3n1 (SBC control unit), internal fault — As C226F. | High |
| C258F | Control unit A7/3n1 (SBC control unit), internal fault — As C226F. | High |
| C26F5 | Control unit A7/3n1 (SBC control unit), internal fault — As C226F. | High |
| C24DB | Fault in CAN communication with control unit N47-5 (ESP control unit) — Common after fitting a unit with the wrong part number. Check the label match first. | Medium |
Descriptions follow Mercedes-Benz's own diagnostic fault wording for the SBC system (checked September 2026); the notes are ours from the bench. Codes from other brake systems are not listed.
Understanding Warnings
"Service Brake Visit Workshop" in grey/white indicates the system is in backup mode. Reduced braking to front wheels only. You can drive carefully but arrange repair urgently.
A RED brake warning indicates a serious fault. STOP IMMEDIATELY. Do not attempt to drive. Pull over safely and arrange vehicle recovery.
Next Steps
If you've scanned your Mercedes and found any of these fault codes, contact us with:
We'll advise on the best repair option for your situation: