Code Details
| Display code | WABCO RSSplus SID 5 FMI 1 |
|---|---|
| SPN | Not applicable or not verified |
| FMI | 1 |
| OEM code | WABCO / ZF SID 5 FMI 1 |
| Manufacturer | WABCO / ZF |
| System | Trailer ABS / RSSplus |
| Component | Wheel Sensor e |
| Source address | Unknown or not applicable |
| Severity | high |
| Review status | ai source checked |
| Source confidence | high |
| Last reviewed | 2026-04-09 |
Plain-English Meaning
The trailer ABS controller is receiving a weaker-than-expected signal from wheel sensor E. On passive magnetic sensors, this typically points to the air gap between the sensor tip and the tone ring being too large. On active sensors, a low signal may indicate a failing sensor or a voltage supply issue to the sensor circuit.
WABCO MM-0888 FMI 1 corresponds to a signal amplitude or voltage below the lower detection threshold for Wheel Sensor e. The RSSplus ECU monitors signal level in addition to frequency. An excessively large air gap, a weak magnetic field in a passive sensor, or a low supply voltage on an active sensor are the typical causes.
Common Symptoms
- Trailer ABS amber lamp active or blinking during pre-trip or while moving
- Wheel sensor E reads an abnormally low signal level in WABCO PC diagnostics
- ABS may be partially or fully inhibited on the affected axle
- Code may be intermittent if the air gap is borderline acceptable at one wheel position
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Air gap between sensor E tip and tone ring is outside specification — most common cause
- Passive sensor magnet has weakened over time or after physical impact
- Tone ring mounted at incorrect depth, off-center, or with excessive runout
- Active sensor supply voltage is low due to wiring resistance or a power issue on the sensor circuit
First Checks
- Confirm WABCO RSSplus SID 5 FMI 1 is active or pending in WABCO PC diagnostics before inspecting.
- Inspect the wheel-end at position E: check the sensor-to-tone-ring air gap against WABCO specification — typically 0.1–1.5 mm for passive sensors depending on the tone ring type.
- Inspect the tone ring for damage, runout, or incorrect installation depth that could reduce signal amplitude.
- If the sensor gap is correct and the tone ring is undamaged, check the harness for high-resistance connections that could affect signal level on active sensors.
Can I Keep Driving?
Trailer ABS and brake-related codes should be handled conservatively. Stop safely for brake warnings, red stop lamps, abnormal braking, wheel-end concerns, or any severe warning condition, and follow fleet or OEM guidance.
Related Lookup Pages
Sources
- WABCO RSSplus Trailer ABS Maintenance Manual MM-0888 WABCO / ZF Commercial Vehicle Solutions · oem · accessed 2026-05-05 · confidence high
Source: WABCO / ZF Commercial Vehicle Solutions, WABCO RSSplus Trailer ABS Maintenance Manual MM-0888. 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
Why does WABCO RSSplus SID 5 FMI 1 appear only at low speed?
Passive wheel speed sensors generate a signal proportional to rotational speed. At low speed, the signal amplitude is already at its minimum. A sensor with a borderline-large air gap may produce acceptable signal at highway speed but fall below the ECU's threshold at low speed, causing the code to set only during stops or slow maneuvers.
Can adjusting the sensor position fix WABCO RSSplus SID 5 FMI 1?
On installations where the sensor bottoms against a mounting surface and relies on the correct hub depth for gap setting, adjustment may not be possible — the tone ring or hub depth would need to be corrected. On installations with an adjustable mounting, the sensor can be advanced to reduce the gap. Consult WABCO installation requirements for the specific trailer axle type.
Does WABCO RSSplus SID 5 FMI 1 mean ABS will not work on wheel E?
ABS function may be inhibited on the affected axle or wheel position when the ECU cannot obtain a reliable speed signal. The trailer ABS lamp active state and the specific ABS inhibit behavior depend on how the RSSplus system is configured and whether a full signal loss or only a low-signal condition is present.