Automatic Day/Night Mirror Test

For circuit descriptions and diagrams, refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.
1. Check the fuse in the intelligent power module. If OK, go to Step 2. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
2. Turn the ignition switch to the ON position. Check for battery voltage at the fuse in the intelligent power module. If OK, go to Step 3. If not OK, repair the open circuit to the ignition switch as required.
3. Unplug the wire harness connector from the automatic day/night mirror. Check for battery voltage at the fused ignition switch output circuit cavity of the automatic day/night mirror wire harness connector. If OK, go to Step 4. If not OK, repair the open circuit to the junction block as required.
4. Turn the ignition switch to the OFF position. Check for continuity between the ground circuit cavity of the automatic day/night mirror wire harness connector and a good ground. There should be continuity If OK, go to Step 5. If not OK, repair the circuit to ground as required.
5. Turn the ignition switch to the ON position. Set the parking brake. Place the transmission gear selector lever in the Reverse position. Check for battery voltage at the backup lamp switch output circuit cavity of the automatic day/night mirror wire harness connector. If voltage is present, reinstall the automatic day/night mirror wire harness connector and go to Step 6. If not OK, repair the open circuit as required.
6. Place the transmission gear selector lever in the Neutral position. Place the automatic day/night mirror switch in the ON (LED in the switch is lighted) position. Cover the forward facing ambient photocell sensor to keep out any ambient light.

NOTE: The ambient photocell sensor must be covered completely, so that no light reaches the sensor. Use a finger pressed tightly against the sensor, or cover the sensor completely with electrical tape.

7. Shine a light into the rearward facing headlamp photocell sensor. The automatic day/night mirror should darken. The automatic day/night mirror should darken within 2 minutes if testing for the first time. For immediate response, turn the vehicle OFF and back ON with the forward-facing light sensor still covered. This defeats the day-detect logic. If OK, go to Step 8. If not OK, replace the faulty mirror unit.
8. With the mirror darkened, place the transmission gear selector lever in the Reverse position. The automatic day/night mirror should return to its normal reflectance. If not OK, replace the faulty mirror unit.

Bench testing both mirrors can be done, of care is exercised. For an inside mirror, the pin closest to he mount is 12V (+), the next is 12V (-). The third is reverse override. The fourth is outside mirror (+), and the fifth is outside mirror (-). Do not apply 12 volts to the fourth and fifth pins. With 12 volts on pins 1 and 2, the mirror can be tested by blocking the rear sensor and shining a light into the forward sensor. For an outside mirror, there is a 2-pin connector. Applying 1.2 volts will cause the mirror to dim. If the mirror does not dim, the entire glass assembly can be replaced just as it is when the glass is broken.

WARNING: DO NOT APPLY 12 VOLTS TO THE OUTSIDE MIRROR. DAMAGE TO THE MIRROR WILL RESULT.