Code Details
| Display code | WABCO MM-0112 SPN 793 FMI 10 |
|---|---|
| SPN | 793 |
| FMI | 10 |
| OEM code | WABCO / ZF SID 5 |
| Manufacturer | WABCO / ZF |
| System | ABS / ESC |
| Component | Left 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 a signal dropout at the left-side third axle wheel speed sensor — FMI 10 means the ECU detected that the signal disappeared or dropped to a non-readable level intermittently. Unlike FMI 5 (open circuit, which is typically constant), FMI 10 is an intermittent condition: the signal is normally present but drops out at certain speeds, temperatures, or road conditions. High-resistance joints, marginal sensor gap, or a partially broken wire that contacts intermittently are typical causes.
The WABCO MM-0112 table maps SPN 793 FMI 10 and SID 5 to Left Third Axle WSS / wheel-speed sensor signal drop-out. This page paraphrases the factual mapping and does not reproduce WABCO troubleshooting procedures.
Common Symptoms
- ABS warning lamp that may come and go rather than being continuously on
- Code may be stored rather than active when the vehicle is stationary — it set during driving and cleared after the wheel stopped
- WABCO diagnostic software may require a test drive to replicate the dropout event
- May appear more frequently at higher road speeds or in specific temperature ranges
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Intermittent open in the sensor wiring — a wire with a partial break that makes contact at rest but opens under vibration or flex
- Corroded connector terminal with high resistance that allows normal signal at low wheel speeds but causes dropout at higher signal frequencies
- Marginal sensor air gap that produces adequate signal at low speeds but insufficient amplitude at higher wheel speeds when signal frequency increases
- Sensor internal intermittent fault — partial coil failure that manifests under heat or vibration rather than at rest
First Checks
- Record the SPN/FMI, active or stored status, and whether the code set while driving or was already stored at the time of inspection.
- Wiggle-test the sensor connector and harness while monitoring the channel in WABCO TOOLBOX live data — a dropout during wiggling confirms a connection fault.
- Check sensor air gap; a gap at the high end of specification may produce adequate signal at idle but drop out at highway wheel speeds.
- Inspect the harness for any area where a partial break could flex open at vehicle speed but contact at rest — pay attention to areas near suspension pivot points or tight harness bends.
- Consider a WABCO TOOLBOX road test with live data logging if the fault cannot be replicated at rest — some dropout codes require dynamic conditions to reproduce.
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
Is WABCO MM-0112 SPN 793 FMI 10 an intermittent fault that I can ignore for now?
An intermittent dropout means the ABS ECU cannot always read valid speed data from this wheel, which can affect ABS modulation quality during a braking event — precisely when reliable data is needed most. Intermittent ABS faults should be diagnosed rather than deferred.
How is FMI 10 different from FMI 2 (erratic signal) on a WABCO sensor?
FMI 2 means the signal is continuously erratic or incorrect — the sensor is present but sending bad data. FMI 10 means the signal was correct but intermittently disappeared entirely. The distinction can guide the diagnostic direction: FMI 2 often points to tone ring or mechanical issues; FMI 10 often points to a marginal electrical connection or partial wire break.
Will the code clear if I ignore it and drive for a while?
A stored code may not show as active at a stop, but the underlying intermittent fault remains. If the condition that caused the dropout recurs during braking, ABS performance can be affected. Clearing the code without repairing the fault is not a resolution.