Circuit/System Description
Backup Lamps (without T90)
The gear position sensor is a switching transistor mounted to the top of the transmission extension housing. The four wire sensor interfaces directly with the Engine Control Module (ECM). The ECM supplies 5 V to the gear position sensor on a 5 V reference circuit and also provides a ground path on a low reference circuit. The sensor provides a pulse width modulated duty cycle to the ECM on two signal circuits that are proportional to the linear and radial position of the corresponding magnet assembly mounted to the shift shaft. With the engine running and the transmission in the reverse position, the ECM responds by sending a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position.
With the engine running and the transmission in the reverse position, the backup lamp switch signal circuit is pulled low and the ECM responds by sending a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position. The BCM applies battery voltage to the backup lamps control circuit illuminating the backup lamps. Once the driver moves the gear selector out of the reverse position, a message is sent by the ECM via serial data requesting the BCM to remove battery voltage from the backup lamps control circuit. The engine must be running for the backup lamps to operate.
Backup Lamp (with T90)
The gear position sensor is a switching transistor mounted to the top of the transmission extension housing. The four wire sensor interfaces directly with the Engine Control Module (ECM). The ECM supplies 5 V to the gear position sensor on a 5 V reference circuit and also provides a ground path on a low reference circuit. The sensor provides a pulse width modulated duty cycle to the ECM on two signal circuits that are proportional to the linear and radial position of the corresponding magnet assembly mounted to the shift shaft. With the engine running and the transmission in the reverse position, the ECM responds by sending a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position.
With the engine running and the transmission in the reverse position, the backup lamp switch signal circuit is pulled low and the ECM responds by sending a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position. The BCM responds to the backup lamp request by applying ground to the backup lamp relay control circuit which energizes the backup lamp relay. With the backup lamp relay energized, the switch contacts close allowing battery voltage to flow through the backup lamp fuse. Battery voltage is then applied from the fuse through the backup lamp control circuit illuminating the backup lamp. Once the driver moves the gear selector out of the reverse position, a message is sent by the ECM via serial data requesting the BCM to remove battery voltage from the backup lamp relay control circuit turning off the backup lamp. The engine must be running for the backup lamps to operate.