CIRCUIT OPERATION
DEFENDER 90 NAS
11
OTHER FEATURES
Rough road detection ECU
When running on rough roads, it is possible for a false indication of engine misfire to be
detected by the ECM. To prevent false fault codes being stored in the ECM, a rough road
detection ECU is fitted to the vehicle. When the rough road detection ECU signals rough
road conditions, the ECM temporarily ignores engine misfire signals.
The rough road detection ECU monitors and compares the speed of all 4 wheels. When
the vehicle is traveling on rough roads, the wheels will rotate at varying speeds as
obstacles are negotiated and wheel slippage occurs. The variance in wheel speeds is
detected by the ECU which signals rough road conditions to the ECM.
Inertia switch
Power to the fuel pump is supplied via the inertia switch. In the event of extreme
deceleration, as would be experienced in a collision, the inertia switch trips, isolating
electrical supply from the fuel pump. The switch is reset by pressing the rubber button on
top of the switch.