Circuit Description
The Body Control Module (BCM) controls the battery guard relay by grounding the relay coil. Once the relay is energized it supplies battery power to the following components:
| • | The Radio Receiver |
| • | The Radio Interface Module (RIM) |
| • | The Fuel Tank Filler Door Relay Coil |
| • | The Rear Compartment Lid Release Relay Coil |
| • | The Cellular Telephone (if equipped) |
When the ignition switch is turned to the LOCK position the BCM transitions to the High Power Mode. In this mode, the BCM is still in control of the battery guard relay and will continue to supply battery power for 15 minutes to the previously mentioned components.
The 15 minute time period is restarted when the BCM receives the following inputs:
| • | An ignition switch transition (LOCK to ON) has occurred while the BCM was asleep. |
| • | The BCM is awake (with the ignition in the LOCK position) and any of the following has occurred: |
| - | The trunk is opened or closed |
| - | A door is opened or closed |
| - | A RFA-Button report is received (Class 2 or RF message) |
| - | Key is placed in the ignition |
| - | The interior light switch is activated |
| • | The BCM is awake and the ignition switch transitions from ON to LOCK. |
Conditions for Setting the DTC
The BCM monitors the output to the battery guard relay every second. The fault code is set when the feedback goes high (short to B+) for 2 seconds.
Action Taken When the DTC Sets
| • | The High Power Mode is deactivated. |
| • | Stores a DTC B1973 in the BCM memory. |
Conditions for Clearing the DTC
| • | The BCM does not detect the malfunction for one monitoring cycle. |
| • | A history DTC will clear after 50 consecutive ignition cycles if the fault is no longer present. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Body Control System Schematics | |||
1 | Perform the Diagnostic System Check for the system exhibiting symptoms. Did you perform the Diagnostic System Check for the system exhibiting symptoms? | Go to Step 2 | Go to Diagnostic System Check for the system exhibiting symptoms |
2 |
Is the DTC retrieved a current DTC? | Go to Step 3 | Go to Step 5 |
3 | Test the relay control circuit for a short to battery. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 4 |
4 | Inspect the BCM connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 |
5 | Inspect the Multifunction Relay connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the concern? | Go to Step 8 | Go to Step 7 |
6 |
Important: Perform the set up procedure for the BCM. Replace the BCM. Refer to Body Control Module Replacement . Did you complete the replacement? | Go to Step 8 | -- |
7 | Replace the Multifunction Relay. Is the replacement complete? | Go to Step 8 | -- |
8 |
Does the BCM operate properly? | System OK | Go to Step 1 |
