Daytime Running Lamp: Description and Operation

Circuit Operation

Daytime Running Lamp (DRL)
The Daytime Running Light system consists of the DRL Module and the DRL Relay.

When the ignition switch is in the ON position, battery voltage is applied to terminal #1 (LG/Y) of the DRL Module through the 10 A TURN FUSE. The DRL module is grounded constantly through terminal #5 (B).

With the ignition switch in the ON position, battery voltage is supplied to the DRL Relay coil at terminal #4 (L) through the 15 A WIPER FUSE. The ground side of the DRL Relay (terminal #1 - (G) is controlled by the DRL Module at terminal #10(G).

The DRL Module monitors the following inputs to control DRL functions to the headlights and the running lights:
- Generator output (terminal #8 - W/R)
- TNS Relay output (terminal #6 - R/L)
- Headlight Relay output (terminal #2 G/R)
- Parking Brake position (ON/OFF)(terminal #11 - L/W)

When the DRL Module senses battery voltage from the TNS Relay, it supplies battery voltage to the running light circuits through the LH and RH 10 A TAIL fuses in the Engine Compartment Fuse/Relay Box at terminal #12 (R/L).

When the DRL Relay is in the neutral position (no input from the Headlight Relay), the contacts in the internal switch closes the circuit between terminals #6 (R) and #2 (R). In this condition the Headlight Switch in the Combination Switch controls the Headlights ON/OFF function. When the DRL Module senses Generator output, and both the Headlight Relay input and the Parking Brake Switch input voltages are 0 V, it grounds the coil in the DRL Relay. In this condition, the DRL Relay switch closes the circuit between terminals #3 (L/B) and #2 (R) bypassing the Headlight switch and supplying battery voltage to the headlights directly from the 25 A HEAD fuse. Also, when the DRL Module senses Generator output the ground path at terminal #3 (L/B) for the Generator Light opens turning OFF the indicator light.