Sierra 1500 2WD V6-4.3L (2008)
3. Position the engine wiring harness lower electrical connector and engage the retainer (3) securing the lower connector (4) to the ECM.
4. Position the engine wiring harness upper electrical connector and engage the retainer (2) securing the upper connector (1) to the ECM.
5. Connect the negative battery cable.
6. If a NEW ECM was installed, program the ECM. See: Testing and Inspection/Programming and Relearning