Code Details
| Display code | WABCO RSSplus SID 6 FMI 3 |
|---|---|
| SPN | Not applicable or not verified |
| FMI | 3 |
| OEM code | WABCO / ZF SID 6 FMI 3 |
| Manufacturer | WABCO / ZF |
| System | Trailer ABS / RSSplus |
| Component | Wheel Sensor f |
| 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 RSSplus ECU has detected that the signal or return wire for sensor F is being pulled toward supply voltage rather than the expected signal level. This points to a wiring fault — specifically, an insulation break or chafed wire that allows the sensor circuit to contact a powered circuit in the harness or chassis.
WABCO MM-0888 FMI 3 maps to a circuit voltage above the upper normal threshold for Wheel Sensor f. On active sensors with a differential signal pair, this can also indicate a broken signal wire where the circuit floats to a bias voltage. On passive sensors, the signal voltage tracks wheel speed; a high-voltage short would exceed the ECU's acceptable range.
Common Symptoms
- Trailer ABS lamp on — typically persistent rather than intermittent
- Sensor F reads abnormally high voltage in WABCO PC diagnostics, possibly max-pegged
- ABS likely inhibited on the affected wheel position
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Sensor signal wire chafed against a powered circuit (trailer power, lighting, or ABS valve harness) — most likely cause
- Connector pin migration causing signal wire contact with a power pin
- Damaged sensor with an internal short to the supply side of its internal circuit (active sensors)
First Checks
- Disconnect the sensor F connector and measure voltage on the ECU-side wire with the trailer powered — a reading above the sensor's expected output range confirms a short to supply in the wiring.
- Inspect the entire harness run from the ECU to the wheel end for chafing, heat damage, or contact with powered wiring.
- Check connector pin alignment — ensure no migration or cross-contact between the signal wire and the power supply pin.
- If the wiring checks out, test the sensor in isolation to rule out an internal sensor short.
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 moisture cause WABCO RSSplus SID 6 FMI 3?
Moisture in a connector can create a low-resistance path between pins, including between the signal pin and a power supply pin if they are adjacent. A short-to-supply from moisture is typically intermittent and may correlate with wet conditions or recent washing. Inspect connectors for water entry, corrosion, and sealing integrity.
Is a shorted sensor or shorted wire more likely for WABCO RSSplus SID 6 FMI 3?
In most field cases, a wiring or connector issue — chafing, pin migration, moisture — is more common than an internal sensor fault. Disconnecting the sensor and re-testing the harness in isolation is the reliable way to determine which side of the connector has the fault.
Will WABCO RSSplus SID 6 FMI 3 set for both signal wires on a differential active sensor?
On active sensors with a differential output pair, a short-to-supply on one wire changes the differential, but the ECU may code it as a single FMI 3 rather than two separate conditions. Check both signal wires at the harness and at the sensor connector.