Rough Road Sensor: Description and Operation

Rough Road Sensor / Accelerometer

The piezo-electric accelerometer is used to detect unevenness in the road surface which is transferred to the engine via the sub-frame. When unevenness exceeds a certain level, misfire diagnosis is disabled.

The accelerometer receives 5V from the engine control module (ECM). Its output signal is approximately 2.5V for a stationary car. When there is vertical movement the signal will oscillate around 2.5V. The accelerometer is mounted on the sub-frame.