Code Details
| Display code | WABCO MM-0112 SPN 794 FMI 5 |
|---|---|
| SPN | 794 |
| FMI | 5 |
| OEM code | WABCO / ZF SID 6 |
| Manufacturer | WABCO / ZF |
| System | ABS / ESC |
| Component | Right Third Axle WSS |
| Source address | Unknown or not applicable |
| Severity | high |
| Review status | ai source checked |
| Source confidence | high |
| Last reviewed | 2026-03-31 |
Plain-English Meaning
This WABCO ABS code flags an open circuit condition in the right-side third axle wheel speed sensor. FMI 5 means the ABS ECU is not detecting any circuit load at the sensor connection — the signal path is broken somewhere between the sensor and the ECU. A broken wire, a connector that has separated, or a sensor with a severed internal element are typical causes.
The WABCO MM-0112 table maps SPN 794 FMI 5 and SID 6 to Right Third Axle WSS / wheel-speed sensor open circuit. This page paraphrases the factual mapping and does not reproduce WABCO troubleshooting procedures.
Common Symptoms
- ABS warning lamp active, typically illuminating shortly after engine start
- No valid wheel speed signal from the right-side third axle position
- WABCO diagnostic software will confirm the open circuit condition at this wheel channel
- Especially common after wheel-end service, tire work, or axle shaft removal
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Wire break in the Right Third Axle WSS signal or power circuit — can result from abrasion, impact, or fatigue cracking from repeated flex
- Connector separation: the wheel-end connector pulled apart, corroded, or lost its latch during service or from road vibration over time
- Sensor element open internally — the coil inside the sensor broke, typically from physical impact or prolonged vibration fatigue
- Terminal pushed back in the connector housing, breaking the circuit without visible external damage
First Checks
- Record all codes, active status, and warning lamp state before touching anything.
- Physically inspect the wheel-end connector first — look for a disconnected plug, a connector that is partially latched, or a pulled-out sensor body at the wheel end.
- Use a multimeter to check continuity in the sensor circuit from the ECU harness end to the sensor connector: no continuity confirms a break in the wiring; continuity confirmed but fault still present points to an ECU connector or internal ECU issue.
- Measure sensor resistance across the sensor terminals with it disconnected — an open reading (infinite resistance) confirms a failed sensor element; a resistance in spec shifts attention to the wiring.
- Trace the harness for any pinch points, cut locations, or areas where the harness was disturbed during recent service.
Can I Keep Driving?
ABS and brake-system codes are safety-related. Stop safely when the red stop lamp is on, braking feels abnormal, or stability control warnings are active. Do not bypass or disable brake or stability systems.
Related Lookup Pages
Sources
- WABCO ABS and E Version Hydraulic ABS Maintenance Manual MM-0112 WABCO / ZF Commercial Vehicle Solutions · oem · accessed 2026-05-05 · confidence high
Source: WABCO / ZF Commercial Vehicle Solutions, WABCO ABS and E Version Hydraulic ABS Maintenance Manual MM-0112. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - TOOLBOX PLUS Diagnostic Software ZF Commercial Vehicle Solutions · oem · accessed 2026-05-05 · confidence medium
Source: ZF Commercial Vehicle Solutions, TOOLBOX PLUS Diagnostic Software. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
Does WABCO MM-0112 SPN 794 FMI 5 mean the wire is definitely broken?
FMI 5 (open circuit) means no circuit load was detected — which is consistent with a broken wire, but also with a disconnected connector, a terminal that backed out, or a sensor coil that has opened internally. A multimeter continuity test from the ECU harness to the sensor connector will identify which segment of the circuit is open.
Is FMI 5 more likely to be wiring or sensor failure?
In the field, connector separation and wiring breaks are more common than sensor coil failure — particularly on high-mileage vehicles or after wheel-end work. Start with a physical and connector inspection before measuring sensor resistance.
Can I drive with this code active?
ABS function at the affected wheel is unavailable. Plan to have the fault diagnosed before operating in conditions where ABS would be needed. Check for any red stop lamps or abnormal brake behavior that would require stopping immediately.