Battery voltage is supplied at all times to the coil and switch sides of the TAIL LAMP Relay from Circuit Breaker 19 located in the I/P fuse block-2. When the headlamps are turned ON, ground from G400 is applied to through the tail lamp relay control circuit energizing the relay. With the relay energized, battery voltage is applied through the switch side of the relay and the park/tail lamp control circuits illuminating all park, tail, clearance, and marker lamps. All components are grounded via G400.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, turn the headlamp switch to the headlamps ON position. The headlamps should illuminate.

⇒	If the headlamps do not illuminate, refer to Headlamps Malfunction .

2. Ignition ON, command the park lamps ON and OFF using the headlamp switch. The park, tail, clearance, and marker lamps should turn ON and OFF when changing between commanded states.

⇒	If all of the lamps do not turn ON and OFF as specified, refer to Tail Lamp Relay Malfunction.

⇒	If one or more of the lamps do not illuminate, refer to Park or Tail Lamp Malfunction.

Tail Lamp Relay Malfunction

1. Ignition OFF, disconnect the tail lamp relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

4. Headlamp switch OFF, connect a test lamp between the relay control circuit terminal and B+. The test lamp should not illuminate.

⇒	If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, test or replace the turn signal multifunction switch.

5. Turn the headlamps ON, The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the turn signal multifunction switch.

6. Connect a 10A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay switch control circuit terminal 87. The park lamps should illuminate.

⇒	If the park lamps do not illuminate, test the control circuit for a short to ground or an open/high resistance.

7. If all circuits test normal, test or replace the turn tail lamp relay.

Park or Tail Lamp Malfunction

1. Ignition OFF, disconnect the harness connector at the inoperative park, tail, clearance, or marker, lamp assembly.
2. Test for less than 5.0 ohms between the ground circuit terminal of the appropriate component listed below and ground.

•	Left or right park lamp assembly terminal B

•	Left or right tail lamp assembly terminal E

•	Clearance lamps terminal B

•	Door marker lamps terminal 3

•	Outside rearview mirror clearance lamps terminal B

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal of the appropriate component listed below and ground.
4. Ignition OFF, command park lamps ON and OFF using the turn signal multifunction switch. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, test or replace the tail lamp relay.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.

5. If all circuits test normal, test or replace the bulb or lamp assembly.

Relay

1. Ignition OFF, disconnect the appropriate relay.
2. Test for 70-100 ohms of resistance between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the appropriate relay.

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the appropriate relay.

4. Test for less than 2.0 ohms of resistance between terminals 30 and 87A.

⇒	If greater than the specified range, replace the appropriate relay.

5. Install a 10A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms of resistance between terminals 30 and 87.

⇒	If greater than the specified range, replace the appropriate relay.

Headlamp Switch

1. Ignition OFF, disconnect the harness connector X1 at the turn signal multifunction switch.
2. Test for infinite resistance between the ground circuit terminal 1 and the control circuit terminals listed below.

•	Terminal 2

•	Terminal 4

⇒	If not the specified value, replace the turn signal multifunction switch.

3. Test for infinite resistance between control circuit terminal 3 and the ground circuit terminal 5.

⇒	If not the specified value, replace the turn signal multifunction switch.

4. Test for less than 2.0 ohms between the control circuit terminal 2 and the ground circuit terminal 5 with the headlamp switch in the PARK position.

⇒	If greater than the specified value, replace the turn signal multifunction switch.

5. Test for less than 2.0 ohms between the control circuit terminal 4 and the ground circuit terminal 5 with the headlamp switch in the ON position.

⇒	If greater than the specified value, replace the turn signal multifunction switch.

6. Test for less than 2.0 ohms between the control circuit terminal 3 and the ground circuit terminal 5, with the dimmer switch in the high beam position.

⇒	If greater than the specified value, replace the turn signal multifunction switch.

7. Test for less than 2.0 ohms between the control circuit terminal 3 and the ground circuit terminal 5 while operating the flash to pass function, using the turn signal multifunction switch.

⇒	If greater than the specified value, replace the turn signal multifunction switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.