G Sensor

The powertrain control module (PCM)/engine control module (ECM) receives rough road information from G sensor. The PCM/ECM uses rough road information to enable or disable misfire diagnostic. The misfire diagnostic can be greatly affected by crankshaft speed variations caused by driving or rough road surfaces. The G sensor generates rough road information by producing a signal which is proportional to movement of a small metal bar inside sensor.

If a fault occurs which causes PCM/ECM to not receive rough road information between 30 and 80 mph (50 and 132 km/h), DTC P1391 will set.