Headlights/Daytime Running Lights (DRL) Circuit Description DeVille
Daytime Running Lamps (DRL)
The PZM will not activate the daytime running lamps (DRL) feature if the headlamps have already been turned on through the headlamp switch or the twilight sentinel.
Battery positive voltage (B+) is applied at all times to the switch side of the DRL relay through CKT 1640 (ORN). When the ignition switch is in the RUN position, the ambient light sensor indicates daytime conditions, and the gear selector is not in the PARK position, a message is sent from the instrument cluster to the body control module (PZM) via the Class 2 serial data line to activate the daytime running lamps (DRL). With the ignition switch in the RUN position, battery positive voltage (B+) is applied to the coil side of the DRL relay via CKT 439 (PNK). When the PZM receives a message from the instrument cluster to activate the DRL, the PZM provides a ground for the coil of the DRL relay via CKT 592 (LT GRN/BLK). The coil is then energized closing the normally open switch contacts. Battery positive voltage (B+) is then applied through the DRL Fuse cavity B9, the DRL relay, the daytime running lamps (DRL) resistor via CKT 589 (GRY), and DRL Fuse cavity D1 via CKT 12 (TAN/BLK) to the L HDLP LO Fuse and the R HDLP LO fuse through CKT 12 (TAN), which feed the LH low beam headlamp and the RH low beam headlamp respectively. The ground is provided to both headlamps from G101. The daytime running lamps (DRL) resistor creates a voltage drop to both the LH and the RH low beam headlamps. This voltage drop causes the low beam headlamps to illuminate at a reduced intensity.
Daytime Running Lamps (DRL) (Eldorado)
The PZM will not activate the daytime running lamps (DRL) feature if the headlamps have already been turned on through the headlamp switch or twilight sentinel.
Battery positive voltage (B+) is applied at all times to the switch side of the DRL relay via CKT 1640 (ORN). When the ignition switch is in the RUN position, the ambient light sensor indicates daytime conditions, and the gear selector is not in the PARK position, a message is sent from the instrument cluster to the body control module (PZM) via the Class 2 serial data line to activate the daytime running lamps (DRL). With the ignition switch in the RUN position, battery positive voltage (B+) is applied to the coil side of the DRL relay via CKT 439 (PNK). When the PZM receives a message from the instrument cluster to activate the DRL, the PZM provides a ground for the coil of the DRL relay via CKT 592 (LT GRN/BLK). The coil is then energized closing the normally open switch contacts. Battery positive voltage (B+) is then applied through the DRL relay to the LH high beam headlamp and the RH high beam headlamp, which are in series. Ground is provided to both headlamps from G101. The LH and RH high beam headlamps will then illuminate at half intensity because they are in series.
Headlights/Daytime Running Lights (DRL) Circuit Description Eldorado
Daytime Running Lamps (DRL)
The PZM will not activate the daytime running lamps (DRL) feature if the headlamps have already been turned on through the headlamp switch or twilight sentinel.
Battery positive voltage (B+) is applied at all times to the switch side of the DRL relay via CKT 1640 (ORN). When the ignition switch is in the RUN position, the ambient light sensor indicates daytime conditions, and the gear selector is not in the PARK position, a message is sent from the instrument cluster to the body control module (PZM) via the Class 2 serial data line to activate the daytime running lamps (DRL). With the ignition switch in the RUN position, battery positive voltage (B+) is applied to the coil side of the DRL relay via CKT 439 (PNK). When the PZM receives a message from the instrument cluster to activate the DRL, the PZM provides a ground for the coil of the DRL relay via CKT 592 (LT GRN/BLK). The coil is then energized closing the normally open switch contacts. Battery positive voltage (B+) is then applied through the DRL relay to the LH high beam headlamp and the RH high beam headlamp, which are in series. Ground is provided to both headlamps from G101. The LH and RH high beam headlamps will then illuminate at half intensity because they are in series.
