First, you should use a DVOM to measure the main relay circuit voltage at the ECM/TCM/IGN fuse in the underhood fuse block and the voltage at the TCM/BATT fuse in the underhood fuse block. Then, you should disconnect the negative battery cable and remove the TCM/BATT fuse and ECM/TCM/IGN fuse from the underhood fuse block. After that, you should disconnect the electrical connectors and record the remaining engine oil life and the remaining automatic transmission fluid life. Finally, you should ensure that there is no main relay circuit voltage (ECM/TCM/IGN Fuse).