Combination Of Substitute

The transmission has two ways of monitoring vehicle speed for shift scheduling and torque converter control. One way is for it to use it's own OSS sensor and the other way to use the individual rear wheel speeds that are transmitted by the ABS module on CAN. If the TCM detects a problem with either of the above signal inputs the transmission will perform all related control functions using the alternative/substitute value. If both systems fail then a double fault DTC will be logged by the TCM.

This DTC logs because two diagnostics with priority 2 have logged simultaneously. The only diagnostics with priority 2 within the TCM software are the OSS (P0720) and ABS wheel speed diagnostics (P1799).