Mirrors: Testing and Inspection

AUTOMATIC DIMMING MIRRORS

For complete circuit 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 fused ignition switch output (run/start) fuse in the Totally Integrated Power Module (TIPM). If OK, go to 2. If not OK, repair the shorted circuit or component as required and replace the ineffective fuse.
2. Turn the ignition switch to the ON position. Check for battery voltage at the fused ignition switch output (run/start) fuse in the TIPM. If OK, go to 3. If not OK, repair the open fused ignition switch output (run/start) circuit to the run-start relay in the TIPM as required.
3. Disconnect the overhead wire harness connector from the automatic dimming inside rear view mirror. Check for battery voltage at the fused ignition switch output (run-start) circuit cavity of the overhead wire harness connector for the mirror. If OK, go to 4. If not OK, repair the open fused ignition switch output (run/start) circuit to the fuse in the TIPM as required.
4. Turn the ignition switch to the OFF position. Check for continuity between the ground circuit cavity of the overhead wire harness connector for the automatic dimming inside rear view mirror and a good ground. There should be continuity. If OK, go to 5. If not OK, repair the open 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 overhead wire harness connector for the automatic dimming inside rear view mirror. If OK, reconnect the overhead wire harness connector to the mirror and go to 6. If not OK, repair the open backup lamp switch output circuit as required.
6. Place the transmission gear selector lever in the NEUTRAL position. Place the automatic dimming inside rear view mirror switch in the ON (green LED indicator illuminated) position. Cover the forward facing ambient photocell light 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 light sensor. The automatic dimming mirror glass should darken within 2 minutes if testing for the first time. For an immediate response, turn the mirror switch to the OFF position and back to the ON position with the forward-facing ambient light sensor still covered. This defeats the daylight detection logic of the mirror. If OK, go to 8. If not OK, replace the ineffective mirror unit.
8. With the mirror darkened, place the transmission gear selector lever in the REVERSE position. The automatic dimming mirror glass should return to its normal reflectance. If not OK, replace the ineffective mirror unit.

BENCH TESTING

Bench testing of both the inside and the driver side outside mirrors can be done if proper care is exercised. Connect the inside mirror ground terminal pin to ground and the fused ignition switch output (run-start) terminal pin to 12 volts. The inside mirror can now be tested by completely blocking the ambient photocell (forward-facing) light sensor and shining a light into the headlight photocell (rearward-facing) light sensor.

CAUTION: In the following test, 1.2 volts is applied to the outside mirror dimming circuits. DO NOT apply 12 volts to these circuits or the mirror dimming circuitry will be damaged and require replacement.

For an outside mirror, there are two pigtail wire circuits (auto day/night mirror plus and auto day/night mirror minus) that are normally controlled by the outputs from the inside mirror circuitry. Applying 1.2 volts to these two circuits should cause the outside mirror glass to darken. If the mirror glass does not darken, the entire mirror glass and case assembly can be replaced just as it is when the glass has been broken. Outside Rearview Mirror - Removal.