For 1990-2009 cars

### Diagnostic Aids

The automatic day-night feature of the inside rearview mirror may not operate properly or become inoperative due to an intermittent short to battery voltage in the backup lamp system.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Inside Rearview Mirror Schematics Connector End View Reference: Mirror Connector End Views
1 | Did you review the operation of the automatic day-night feature of the inside rearview mirror? | -- | Go to Step 2 | Go to Automatic Day-Night Mirror Description and Operation
2 |

1. Turn ON the ignition, with the engine OFF.
2. Enable the automatic day-night feature of the inside rearview mirror.
3. Cover the sensor on the inside rearview mirror back, facing the front window.
4. Shine a bright light into the sensor on the inside rearview mirror face, facing the rear window.

Does the inside rearview mirror darken?

--

Go to Diagnostic Aids

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Disconnect the inside rearview mirror harness connector.
3. Measure the resistance between the ground circuit of the inside rearview mirror and a good ground.

Is the resistance less than the specified value?

3 Ω

Go to Step 4

Go to Step 9

4 |

1. Turn ON the ignition, with the engine OFF.
2. Measure the voltage between the ignition voltage circuit and the ground circuit of the inside rearview mirror.

Is the voltage within the specified range?

B+

Go to Step 5

Go to Step 10

5 |

1. Place the transmission in PARK.
2. Measure the voltage between the backup lamp supply voltage circuit and the ground circuit of the inside rearview mirror.

Is the voltage less than the specified value?

0.5 V

Go to Step 6

Go to Backup Lamps Always On

6 |

1. Place the transmission in REVERSE.
2. Measure the voltage between the backup lamp supply voltage circuit and the ground circuit of the inside rearview mirror.

Is the voltage within the specified range?

B+

Go to Step 8

Go to Step 7

7 | Test the backup lamp supply voltage circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Park Lamps Inoperative
8 | Inspect for poor connections at the harness connector of the inside rearview mirror. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11
9 | Locate and repair an open or high resistance in the ground circuit of the inside rearview mirror. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 12 | --
10 | Locate and repair an open, high resistance, or short to ground in the ignition voltage circuit of the inside rearview mirror. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 12 | --
11 | Replace the inside rearview mirror. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | --
12 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2