Code Details
| Display code | WABCO RSSplus SID 6 FMI 5 |
|---|---|
| SPN | Not applicable or not verified |
| FMI | 5 |
| OEM code | WABCO / ZF SID 6 FMI 5 |
| 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 detected a break in the sensor F circuit. An open circuit means the wiring is effectively disconnected — either a wire has broken internally, a connector has pulled apart, a terminal has backed out of its housing, or the sensor itself has failed open internally. The ECU receives no signal at all rather than a weak or erratic one.
WABCO MM-0888 FMI 5 corresponds to an open-circuit condition on Wheel Sensor f. The ECU applies a bias or excitation to the sensor circuit and monitors for signal return; an open circuit prevents the current path from completing, which is distinguishable from a low-signal condition (FMI 1) because the circuit resistance is unmeasurably high rather than just producing a weak output.
Common Symptoms
- Trailer ABS lamp on, typically persistent from the time the open circuit develops
- Sensor F shows no signal or infinite resistance in WABCO PC diagnostics
- ABS fully inhibited on the affected wheel — open circuit is a definitive fault
Possible Causes
Possible causes may include the items below. The list is not a parts diagnosis.
- Broken wire in the sensor harness — internal strand breaks can occur from flexing at suspension pivot points
- Connector pulled apart at the wheel-end connection or at a mid-harness junction
- Terminal backed out of a Deutsch or AMP connector housing — pin retention clip failure or improper assembly
- Sensor failed open internally — sensor body cracked, corrosion at the terminal interface, or internal wire bond failure
First Checks
- Measure continuity of the sensor F circuit from the ECU connector to the wheel-end connector — an open circuit should show clearly as infinite resistance on a standard multimeter.
- Inspect connector bodies at both ends for pulled-apart housings, bent or pushed-back terminals, and damaged locking tabs.
- Flex the harness through its range of motion at the suspension pivot — a flex-induced break will show as an intermittent open during the flexing test.
- If the harness tests continuous but the fault remains, disconnect the sensor and measure resistance across the sensor terminals — an open-circuit reading confirms sensor failure.
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 corroded terminal cause WABCO RSSplus SID 6 FMI 5?
Yes. Heavy terminal corrosion can increase resistance to the point where the circuit is effectively open — the ECU's bias current cannot complete the circuit through the corroded contact. Clean, bright terminal surfaces and properly sealed connectors prevent this. A terminal that appears visually corroded should be replaced, not just cleaned, for a reliable repair.
Is WABCO RSSplus SID 6 FMI 5 ever intermittent?
Yes. A harness with a cracked wire that is still held together by the insulation may test continuous when static but open when the suspension cycles. Wiggle-testing the harness at known flex points while monitoring the circuit in live data is the most reliable way to catch intermittent open-circuit faults.
Will the trailer ABS lamp stay on continuously with WABCO RSSplus SID 6 FMI 5?
An open circuit on a sensor channel is a persistent fault condition. The ABS lamp will typically remain on until the ECU receives a valid signal from the sensor circuit during a power-on self-test or a motion event. The lamp may go out briefly during a reset but will return if the circuit is still open.