Download 1999-2004 Isuzu NPR/NQR Perform TPS Relearn Procedure – TPS Relearn Procedure If there is a change in the relationship between the TPS and the injection pump rack voltage, there will be a noticeable change in the shift pattern of the transmission. The TPS relearn is needed to provide the TCM with a correlation value between the TPS sensor and the injection pump rack position. It is this learned value that the TCM uses to produce the shift pattern for the transmission based on the TPS input during vehicle operation. The difference in the shift pattern can be anything such as harsh/delayed shift, no shift and slipping (in cases where the TPS sensor voltage exceeds 0.15 volts at WOT, or 4.8 volts at IDLE, the TCM will set DTC 21). This shift pattern change will not cause immediate damage to the transmission. It may result in excessive clutch wear over a prolonged period. Important: There are six simple, but necessary steps to this procedure. Follow these steps in order. The preliminary steps are essential and important to the success of the relearn procedure. If the preliminary steps are NOT followed, the relearn procedure will NOT work.