DTC P0318: Rough Road Sensor Circuit: Description

Correct engine misfire detection is dependent on whether or not the vehicle is experiencing a rough road condition. A rough road condition will cause unexpected crankshaft fluctuations especially when the torque converter clutch is in its lockup state. In order to detect a rough road condition, the ECM will use vehicle speed information from the Right Front Wheel Speed Sensor (RFWSS) available on both ABS and non-ABS vehicles. On ABS vehicles, the Electronic Brake and Traction Control Module (EBTCM) sends the ECM RFWSS signal information over the Controller Area Network (CAN) link. On non-ABS vehicles, the ECM receives this information over a discrete wire from the wheel speed signal conditioner module. This module converts the AC signal from the RFWSS to a square wave by momentarily grounding White wire. The ECM contains an internal 12 volt pull-up voltage supplied to White wire necessary to detect a square wave of 0 to 12 volts. DTC P0318 will set if the ECM does not detect a sufficient rough road signal based on the vehicle speed from the RFWSS when the vehicle is traveling in 4th or 5th gear for a certain length of time. If the ECM does not receive a rough road signal, it will not detect misfire.