Auto Service Professional

DEC 2018

Magazine for the auto service professional

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Page 33 of 61

32 A S P D e c e m b e r 2 018 P u s h B u t t o n S t a r t On this vehicle the power mode master is the BCM. e BCM has multiple battery plus circuits that feed into it. Each of those circuits are par- titioned within the controller to drive certain outputs of the vehicle's body functions. An open or short in any one of the battery plus circuits may induce multiple codes or a section of non- functionality within the BCM with the rest of the BCM functioning normally. In this case it is useful to refer to the power distribution schematics to determine if the non- functional partition of the controller shares a common battery plus circuit. e ignition mode switch is a low current switch with a discrete ignition signal to the pow- er mode master for determination of the power mode that will be sent over the serial data circuits to the other modules that need this information. e power mode master will also activate re- lays and other direct outputs of the power mode master as needed. e power mode master deter- mines which power mode (Off, Accessory, Run, Crank Request) is required, and reports this in- formation to other modules via serial data. Modules which have switched voltage inputs may operate in a default mode if the power mode serial data message does not match what the indi- vidual module can see from its own connections. e keyless entry control module also moni- tors voltage on the switch in the same manner as the BCM, but monitors the second switch located in the ignition mode switch. e keyless entry control module also controls the backup power through the run/crank coil control circuit by applying voltage to the ignition voltage circuit. is circuit is a pass-thru in the BCM and will energize the ignition circuit when the appropri- ate power mode is required. e power mode master receives ignition switch or ignition mode switch signals to identi- fy the operator's desired power mode. e Chev- rolet Traverse has a couple of fuse box or PDC (power distribution centers) that come into play with the push button start system. e battery PDC (see Figure 8) located on top of the battery is a small fuse center with some good sized high amperage fuses. e front PDC center (see Figure 9) is located on the le front inner fender and houses many more fuses as well. ere is another PDC in the rear of the vehicle located behind the le rear inner trim panel. On any vehicle, knowing where the fuse or electrical PDCs are located is essential in diag- Figure 5: Momentarily pressing the ignition mode switch button once will enter the accessory mode and the amber light will illuminate. Figure 6: When in the RUN/Start mode, the green LED will light up.

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