DTC Descriptors
DTC B1640 01: Mirror Heater Circuit Short to Battery
DTC B1640 02: Mirror Heater Circuit Short to Ground
Diagnostic Fault Information
Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
Circuit/System Description
The driver door module (DDM) and passenger door module (PDM) supply voltage to the outside rear view mirror heater elements upon receipt of a GMLAN message from the HVAC control module indicating that the rear defogger system has been activated. The door
modules monitor the heater element control circuits whenever the ignition is on. For more detailed information concerning power mirror operation refer to
Outside Mirror Description and Operation
.
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | DTC B1640 01 will set when the DDM or PDM detects a short to voltage in the heater element control circuit. |
| • | DTC B1640 02 will set when the DDM or PDM detects a short to ground in the heater element control circuit. |
Action Taken When the DTC Sets
The DDM or PDM will not activate the affected heated mirror.
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | You issue a scan tool CLEAR DTCs command. |
| • | A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Outside Rearview Mirror Schematics
Connector End View Reference
Power Door Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the C1 harness connector at the appropriate outside rearview mirror.
- Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal 3 and ground.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the appropriate door control module. |
- Connect a test lamp between control circuit terminal 4 and low reference circuit terminal 3.
- Ignition ON, turn the rear defogger ON and OFF. The test lamp should turn ON and OFF as the rear defogger switch is cycled On and OFF.
| ⇒ | If the test lamp remains OFF, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate door control module. |
| ⇒ | If test lamp remains ON, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the appropriate door control module. |
- If all circuits test normal, test or replace the appropriate outside rearview mirror face.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
