GM Service Manual Online
For 1990-2009 cars only

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.

DTC Descriptor

DTC B1550: Mirror LF/RF Select Switch Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Switch B+

1

1

--

--

Driver Mirror Select Switch Signal

2

2

B1550

--

Driver Mirror Select Switch Signal

2

2

B1550

--

1. Power Mirror Switch Malfunction

2. Mirror Select Switch Malfunction

Circuit/System Description

The driver door module (DDM) supplies battery positive voltage to the power mirror switch. When the mirror select switch is placed in the left or right mirror position, the appropriate signal circuit is switched to B+. The DDM senses the voltage change and allows control of the selected outside rearview mirror.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The DDM senses an active state on both mirror select switch circuits greater than 3 seconds.

Action Taken When the DTC Sets

The DDM ignores the continuous inputs from the switch. The DDM will respond to all other valid switch inputs.

Conditions for Clearing the DTC

    • A current DTC will clear when the fault is no longer present.
    • A history DTC will clear after 40 malfunction-free ignition cycles

Reference Information

Schematic Reference

Outside Rearview Mirror Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Outside Mirror Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool Mirror Select Switch parameter while cycling the mirror select switch between the left and right positions. The parameter should change between Neutral, Left, and Right.

Circuit/System Testing

  1. Ignition OFF, disconnect the X5 harness connector at the DDM.
  2. Ignition ON, verify the scan tool Mirror Select Switch parameter is Neutral.
  3. If not the specified value, replace the DDM.
  4. Ignition OFF, reconnect the X5 harness connector at the DDM.
  5. Ignition ON, observe the scan tool Mirror Select Switch parameter while cycling the mirror select switch between the left and right positions. The parameter should change between Neutral, Left, and Right.
  6. If the parameter does not cycle between the specified values, replace the outside rearview mirror switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Power Mirror Switch Replacement
    •  Control Module References for DDM or PDM replacement, setup, and programming