Perform the Diagnostic System Check - Lighting Systems prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Fog Lamp Relay Control Circuit | 2 | 1 | 1 | -- |
Fog Lamps Supply Voltage Circuit | 1 | 1 | 2 | -- |
1. Fog Lamps Inoperative 2. Fog Lamps Always ON |
When the ignition switch is in the ON position and the headlamp switch is in either PARK or HEAD position, the fog lights illuminate whenever you press the fog lamp switch. The FOG RLY fuse in the top of the engine fuse block supplies battery positive voltage to both the fog lamp relay switch contacts and to the fog lamp relay coil circuit. The fog lamp relay coil is controlled by the body control module (BCM). Whenever you press the fog lamp switch, the BCM fog lamp switch input is grounded. The BCM energizes the control circuit of the fog lamp relay coil. The current flows from the fog lamp relay to both front fog lamps and to ground G101. The fog lamps remain ON until you again press the front fog lamp switch, or until you cycle the ignition switch OFF and ON. The park lamps or low beam headlamps must be ON in order for the fog lamps to be illuminated. Fog lamp operation will be cancelled whenever the park lamps are turned OFF or the high beam headlamps have been selected.
Lighting Systems Connector End Views
Ignition ON, observe the Fog Lamp Switch Input parameter while toggling the fog lamp switch ON and OFF. The reading should change between active and inactive.
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance or short to voltage. |
⇒ | If the voltmeter always displays 0 volts, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the body control module. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, replace the fog lamp relay. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the fog lamp supply voltage circuit for a short to ground. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the fog lamps do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the fog lamp bulbs. |
⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the body control module. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the body control module. |