Rough Road Signal
- Discovery
When vehicle travels over rough terrain, or on rough roads instability becomes apparent in the drive train. The ECM may interpret these vibrations as a "false misfire". To prevent this "false misfire" interpretation the SLABS ECU generates a rough road signal. The rough road signal is sent to the ECM. The ECM can suspend misfire detection for as long as the vehicle is travelling on the "rough road". - Freelander
When vehicle travels over a rough road surface the engine crankshaft is subjected to torsional vibrations caused by mechanical feedback from the road surface through the transmission. To prevent misinterpretation of these torsional vibrations as a misfire, the misfire monitor is disabled when a road surface exceeds a roughness limit programmed into the ECM. The roughness of the road is calculated by the ABS modulator. The ABS modulator receives information from the four ABS sensor inputs. This information is transmitted to the ECM on the CAN bus. - Range Rover
The ABS ECU generates a digital road speed signal from the average speed of the four wheels. The ABS ECU passes the road speed signal to the Body Electrical Control Module (BECM). The BECM outputs the road speed signal to the following:- Engine Control Module (ECM).
- Cruise control ECU.
- Instrument cluster.
- Air Temperature Control (ATC) ECU.
- In-Car Entertainment (ICE).
- Electronic Air Suspension (EAS) ECU.
- Electronic Automatic Transmission (EAT) ECU.
The digital rough road signal is generated from the difference in rotational speed of each wheel.