Chevrolet Silverado / GMC Sierra. Manual — part 2662

Circuit/System Verification

1. Ignition ON, headlamps ON, vehicle in PARK, cover the front light sensor with a towel or

other suitable item. Shine a flashlight at the rear light sensor while observing the inside
rearview mirror face. The inside rearview mirror face should dim.

If the mirror face does not dim, test or replace the inside rearview mirror.

2. Headlamps ON, park brake applied, cover the front light sensor with a towel or other

suitable item. Shine a flashlight at the rear light sensor while observing the inside rearview
mirror face. Place the transmission in REVERSE. The inside rearview mirror face should
transition from dim to bright.

If the mirror does not transition from dim to bright, refer to Reverse Input Malfunction
below.

3. Headlamps ON, vehicle in PARK, cover the front light sensor with a towel or other suitable

item. Shine a flashlight at the rear light sensor while observing the left outside rearview
mirror face. The left outside rearview mirror face should dim.

If the left outside rearview mirror face does not dim, refer to Outside Rearview Mirror
Dimming Malfunction below.

4. Remove the towel from the inside rearview mirror and remove the flashlight. Verify the

inside rearview mirror face returns to its normal bright state.

If the mirror face does not return to its normal state, test or replace the inside rearview
mirror.

Circuit/System Testing

Reverse Input Malfunction

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.

2. Ignition ON, park brake applied, vehicle in REVERSE, test for B+ between the supply

voltage circuit terminal 9 and ground.

If less than the specified value, test the supply voltage circuit for a short to ground or
an open/high resistance. If the circuit tests normal, refer to Backup Lamps
Malfunction .

3. If all circuits test normal, test or replace the inside rearview mirror.

Outside Rearview Mirror Dimming Malfunction

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.

2. Ignition ON, verify a test lamp does not illuminate between the following circuits and

ground:

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Signal circuit terminal 5

Low reference circuit terminal 16

If the test lamp illuminates, test the applicable circuit for a short to voltage.

3. Ignition OFF, test for infinite resistance between the following circuits and ground:

Signal circuit terminal 5

Low reference circuit terminal 16

If less than the specified range, test the applicable circuit for a short to ground.

4. Test for less than 100 ohms of resistance between the signal circuit terminal 5 and the low

reference circuit terminal 16.

If greater than the specified range, test both circuits for an open/high resistance. If the
circuit tests normal, test or replace the driver outside rearview mirror face.

5. If all circuits test normal, replace the inside rearview mirror.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Inside Rearview Mirror Replacement

Outside Rearview Mirror Glass Replacement

AUTOMATIC DAY-NIGHT MIRRORS INOPERATIVE (WITHOUT RPO DL3/DR4)

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Backup Lamp Supply Voltage

1

1

2

-

1. Rearview mirror remains dimmed in reverse
2. Rearview mirror does not dim

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

The inside rearview mirror uses 2 photocell sensors. One sensor is the rear light sensor, located on
the face side of the mirror, facing the rear of the vehicle. The rear light sensor is used to
determine light conditions present at the mirror face. The other sensor is the front light sensor,
located on the backside of the mirror, facing the front of the vehicle. The front light sensor is used
to determine the exterior light conditions at the front of the vehicle. With a low exterior light
condition detected by the front light sensor and a high light condition from the rear light sensor,
the inside rearview mirror will automatically darken the face of the inside rearview mirror.

With the gear selector lever in the REVERSE position, backup lamp supply voltage is supplied as
an input to the inside rearview mirror. The mirror monitors this input to disable the automatic
day-night feature. This allows the driver to see objects in the mirror clearly when backing up,
regardless of the rear light sensor status.

Reference Information

Schematic Reference

Inside Rearview Mirror Schematics

Outside Rearview Mirror Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Day-Night Mirror Description and Operation

Electrical Information Reference

Circuit Testing

Wiper/Washer Schematics

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References For Scan Tool Information.

Circuit/System Verification

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado