Turn Signal Lamps

CONTROL MODULE RESPONSIBILITY

• BCM - Turn signal lights request from the SCCM, received from the turn signal multifunction switch.
• BCM - Turn signal lights powering (left and right sides).
• BCM - Turn signal light status transmittal over CAN-IHS.
• BCM - Combined lighting turn/stop and park/turn lamp management.
• IPC - Obtain turn signal lamp status from CAN-IHS.
• IPC - Turn signal lights signaling management.
• IPC - Turn signal lights fail signaling management.
• SCCM - Turn signal output acquisition from the multifunction switch.
• SCCM - Turn signal activation request to BCM over CAN-C.

The left or right direction signals are activated using the left stalk switch input to the SCCM. These commands are codified using a resistive divider, into the analogical command that is read by the SCCM and then sent to the BCM over CAN-C.

The turn signal lamps system includes the multifunction switch on the steering column, the SCCM, the IPC and the BCM. The front turn signal lamp LED array has a path to ground at all times through their connection to the combination park/turn lamp and dash wire harness. The combination park/turn lamp and dash wire harness has takeouts with eyelet terminals that are secured to the body sheet metal. The rear turn signal lamps are LED elements within the rear outer tail lamp housing.

The SCCM monitors a hard wired multiplex input from the multifunction switch to determine the status of the turn signal switch, then sends the appropriate electronic turn signal switch status messages to the BCM over the CAN data bus. The BCM responds to these messages by controlling a battery voltage output and the flash rate for either the right or left turn signal lamps through high side drivers on the appropriate front and rear, right or left turn signal control circuits. The BCM also sends the appropriate electronic messages to the IPC to control the illumination and flash rate of the right or left turn signal indicators, as well as to control the click rate of an electromechanical relay soldered to the IPC electronic circuit board that emulates the sound emitted by a conventional electromechanical turn signal flasher.

The BCM also provides a Turn Signal ON warning that will send a request message to the IPC over the CAN bus that causes the IPC to generate repetitive chimes to indicate that a turn signal has been active continuously for 1.6 kilometers (1 mile) with the vehicle speed greater than 22 km/h (15 mph). The chime will continue until the turn signal input becomes inactive or until the vehicle speed message indicates that the speed is less than 22 km/h (15 mph), whichever occurs first.

SNA Definition -  Signal Not Acquired (SNA). If the SCCM detects an issue (stuck switch, and others) and sets an active fault, the SCCM shall broadcast the SNA state to the BCM. BCM will default to an idle state and keep all turn signal outputs OFF until a valid request is received.

Combined Rear Lighting -  Some models will be equipped with combined rear lighting. The stop lamp and the turn signal lamp share the same LED Array. When the turn signal is activated, the SCCM recognizes the signal switch request. The SCCM sends this message over the CAN-C bus to the BCM for processing. The BCM then actuates the LED array for signal operation only until the stalk is reset back to the neutral position.

Lane Change Function -  If either of the turn signals are actuated for a time equal to or less than 500ms, the BCM will activate the requested turn signal light and will blink for three blinks. At the same time the signals are switched ON, the BCM will also activate the internal signal corresponding with the selected side. The internal signal will show ON for the entire period of the turn signal event and will not show to be blinking. The internal signal is synchronous with the signal activation and will turn OFF at the end of the event. After three blink cycles, the BCM switches OFF the turn signals, the CAN-IHS signals, and the internal signals corresponding to the selected side.