DTC Descriptor
DTC B3855: Rollover Sensor PerformanceDTC B3856: Discard Rollover Sensor
DTC B3857: Incorrect Rollover Sensor Installed
Diagnostic Fault Information
Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
Serial Data Link Circuit | B3855 | B3855 | B3855 | B3855 | B3855 |
Circuit/System Description
The inflatable restraint vehicle rollover sensor (ROS) utilizes battery power supply and a bidirectional interface circuit. The ROS modulates current on the interface to send ID, State of Health, and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). When the ignition is turned on the ROS responds by performing internal diagnostics and sending an ID to the SDM. The ROS continually communicates status messages to the SDM, which determines if a fault is present in the ROS circuit. If the fault is present, the SDM will set a diagnostic trouble code (DTC).
Conditions for Running the DTC
Ignition voltage is between 9-16 volts.
Conditions for Setting the DTC
B3855
| • | A valid ID message is not received within 5 seconds of the ROS being powered up. |
| • | The SDM has not received a status message. |
B3856
| • | The SDM has received a NOK message from the ROS. |
| • | A ROS internal fault exists for a 127 ignition cycles. |
B3857
The SDM has received an ID message from the ROS that does not match the ID stored in the SDM memory.
Action Taken When the DTC Sets
The SDM commands the AIR BAG indicator ON via serial data communications.
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used. |
| • | A history DTC will clear once 255 malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Circuit/System Testing
- Ignition ON, use a scan tool and check for DTC B3856 or B3857. Verify DTC B3856 or B3857 is not set current.
- Use the scan tool to check for DTC B3855, if DTC B3855 is set current then disconnect the ROS connector. Refer to vehicle rollover sensor replacement in Repair Instructions for connector location.
- Test the ROS ignition 1voltage and ground circuits for an open or high resistance. Verify that a open or high resistance does not exist.
- Remove the SDM connector. Refer to SDM replacement in Repair Instructions for connector location.
- Test the serial data link circuit between the SDM and ROS for a short to voltage, short to ground, or open/low resistance. Verify that a short to voltage, short to ground, or open/low resistance does not exist.
- Reconnect all SIR components. Ignition ON, use the scan tool to clear the DTCs then recheck for DTCs.
Important: When removing connectors inspect for damage or corrosion. Damage or corrosion in the following requires repair or replacement of the affected component/connector.
• The rollover sensor • The SDM module • The rollover sensor wiring harness connector • The SDM wiring harness connector
| ⇒ | If DTC B3856 or B3857 is set current then replace the ROS. Refer to vehicle rollover sensor replacement in Repair Instructions |
| ⇒ | If any of the above conditions are found make the appropriate repair. |
| ⇒ | If any of the above conditions are found make the appropriate repair. |
| ⇒ | If DTC B3855 was current replace the ROS. After replacement refer to Repair Verification. |
Repair Instructions
Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for SDM replacement, setup, and programming |
Repair Verification
Ignition ON, use the scan tool to clear the DTCs then recheck for DTCs.
| ⇒ | If DTC B3855 was current replace the SDM |
