Diagnosis And Testing - Automatic Dimming Inside Rear View Mirror

For complete circuit diagrams, refer to the appropriate wiring information.

1. Ensure that the automatic dimming mirror feature is NOT turned off.
2. With the status of the ignition switch Off, disconnect and isolate the battery negative cable. Unplug the wire harness connector from the ElectroChromic Mirror Module (ECMM). Reconnect the battery negative cable, then transition the status of the ignition switch to ON. Check for battery voltage at the fused ignition output run circuit cavity of the wire harness connector for the ECMM. If OK, go to step 2. If not OK, repair the open circuit as required.
3. Transition the status of the ignition switch to Off. Disconnect and isolate the battery negative cable. Check for continuity between the ground circuit cavity of the wire harness connector for the ECMM and a good ground. There should be continuity. If OK, go to step 3. If not OK, repair the open circuit to ground as required.
4. Connect the wire harness connector for the ECMM. Connect the battery negative cable. Cover the forward facing ambient photocell sensor to keep out any ambient light. Transition the status of the ignition switch to ON. Place the transmission gear selector lever in the N  eutral position.
   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.

5. Shine a light into the rearward facing headlamp photocell sensor. The mirror glass should darken. Turn the light OFF. The mirror glass should return to normal reflectance. If OK, go to step 5. If not OK, replace the ineffective ECMM unit.
6. Use a diagnostic scan tool and the appropriate diagnostic procedure to perform further ECMM diagnosis.