Code Details
| Display code | WABCO RSSplus SID 5 FMI 6 |
|---|---|
| SPN | Not applicable or not verified |
| FMI | 6 |
| OEM code | WABCO / ZF SID 5 FMI 6 |
| 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
Unlike a short to supply (FMI 3) or short to ground (FMI 4) which affect voltage, FMI 6 specifically flags excessive current draw. This means the ECU's sensor supply circuit is being overloaded — either the sensor has developed an internal low-resistance path, or the wiring has a short that is drawing enough current to exceed the circuit's protection threshold.
WABCO MM-0888 FMI 6 maps to an above-normal current condition for Wheel Sensor e. Active sensors supplied with excitation voltage draw a known current range; when a fault creates a low-resistance path in parallel with the sensor's internal resistance, the supply current rises above the upper limit. The ECU monitors supply current and flags the overcurrent condition independently of the voltage.
Common Symptoms
- Trailer ABS lamp on — typically persistent
- Abnormally high current reading on sensor E supply in WABCO PC diagnostics
- ECU may limit or shut off the sensor supply circuit to protect itself
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Active sensor with an internal short — the sensor body has developed a low-resistance fault across its supply and ground
- Wiring short between the sensor supply and ground that allows excessive current to flow without creating a hard short-to-ground voltage fault
- Damaged connector with a bridging fault between supply and ground pins
First Checks
- Disconnect sensor E from the harness. If the high-current condition clears with the sensor disconnected, the fault is inside the sensor.
- Inspect the sensor connector for metal bridging, debris, or insulation damage that could create a partial short between supply and ground pins.
- If the fault persists with the sensor disconnected, inspect the harness for a wiring short between the supply and ground conductors using a resistance check across those two wires.
- Do not attempt to operate the system with a confirmed high-current fault — ECU protection circuits may limit supply indefinitely until the fault is corrected.
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
Can a high-current fault damage the RSSplus ECU?
The RSSplus ECU has internal protection for its sensor supply outputs. In most cases, the ECU will limit or shut down the affected channel rather than sustaining damage. However, a persistent high-current condition is a real stress on the protection circuit, and the fault should be repaired promptly rather than left active.
Is FMI 6 the same as FMI 3 or FMI 4?
No. FMI 3 (shorted to supply) and FMI 4 (shorted to ground) flag voltage deviations. FMI 6 flags current. A wiring fault that creates a low-resistance parallel path across the sensor circuit may produce normal or near-normal voltage readings but still draw excessive current. Both voltage and current monitoring are needed to fully characterize a sensor circuit fault.
Does FMI 6 occur on passive (variable reluctance) wheel speed sensors?
FMI 6 is less common on passive sensors because they are passive inductors with no supply current — the ECU monitors their output voltage directly. High-current faults (FMI 6) are more characteristic of active sensors that have a powered supply circuit. If FMI 6 appears on an application where a passive sensor is fitted, verify the sensor specification matches the ECU's expected sensor type.