Battery Power Off (BPO) Request

The traction battery control module (TBCM) checks the inertia fuel shut off switches, the high voltage interlock (HVIL) circuit, and the traction battery lid tamper switch for an open circuit fault condition. If the open circuit fault condition is not detected, the TBCM continuously toggles the BPO output, typically generating a 2 Hz pulse width modulated signal to the powertrain control module (PCM). The TBCM also broadcasts a normal message to the PCM over the communication link. When the TBCM detects a fault condition, it changes the pulse width modulated signal frequency to 6 Hz at 50% duty cycle and broadcasts an error message to the PCM over the communication link. The error message and the 6 Hz frequency indicate to the PCM that the traction battery opens its contactors in 1 second. After the contactors are open the PCM carries out a normal power down sequence to the transaxle control module (TCM) and DC/DC converter.