Rear Turn Lamps Operation (liftgate open)

WARNING: This page is about a different car, the 2018 Lincoln MKC. However, it is still accessible from the selected car via links, so may be relevant.

When the liftgate is open, the RGTM does not supply a liftgate ajar ground signal to the liftgate mounted LH and RH rear turn lamps and to the auxiliary turn lamps.
When the liftgate mounted LH and RH rear turn lamps sense no ground signal on the ajar signal circuit and voltage on the turn lamp circuit, the liftgate mounted turn lamps do not illuminate.
When the auxiliary turn lamps (part of the rear side marker lamps) sense no ground signal on the ajar signal circuit and voltage on the turn lamp circuit, the auxiliary turn lamps illuminate.

The timed on/off cycle for turn lamps is determined by the BCM and is set to flash approximately 70 times per minute if both the front and rear turn signal lamps operate correctly.

The rear turn lamps are Light Emitting Diodes (LEDs) in the rear lamp assemblies and have an outage circuit that tells the BCM when the Light Emitting Diodes (LEDs) are inoperative. During normal operation, when voltage is applied to the rear turn Light Emitting Diodes (LEDs), the feedback circuit sends the same voltage back to the BCM through the outage circuit. If the Light Emitting Diodes (LEDs) are inoperative the BCM will not receive this voltage feedback through the outage circuit.

If a front or rear turn signal lamp is inoperative, the BCM fast flashes the remaining turn lamp(s) approximately 150 times per minute to indicate a bulb outage to the driver.

The LH multifunction switch has 2 detents for the left turn position and 2 detents for the right turn position. When placed in the first detent and released, the corresponding turn signals flash 3 times and turn off. When the LH multifunction switch is moved to the second detent, the turn signal flashes until the steering wheel is turned in the opposite direction.

The BCM supplies a high current switched voltage to the rear lamp assemblies to supply the necessary current to operate the turn signal Light Emitting Diodes (LEDs). The BCM provides a low current voltage signal to the rear lamp assemblies to switch on the turn signal Light Emitting Diodes (LEDs).

The BCM also provides an Field Effect Transistor (FET) protection of the turn lamp output circuits. When an excessive current draw is detected, the BCM disables the affected turn lamp circuit driver.

Refer to: Module Controlled Functions - System Operation and Component Description .