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).
This diagnostic procedure supports the following DTCs:
• | DTC B3855 Rollover Sensor Performance |
• | DTC B3856 Discard Rollover Sensor |
• | DTC B3857 Incorrect Rollover Sensor Installed |
Ignition 1 voltage is within the normal operating voltage range of 9-16 volts.
• | DTC B3855 will set when one of the following conditions occur: |
- | A valid ID message is not received within 5 seconds of the ROS being powered up. |
- | A status message is not received. |
• | DTC B3856 will set when one of the following conditions occur: |
- | The SDM has received a NOK message from the ROS. |
- | A ROS internal fault exists for a 127 ignition cycles. |
• | DTC B3857 will set when the SDM has received an ID message from the ROS that does not match the ID stored in the SDM memory. |
The SDM commands ON the AIR BAG warning lamp via class 2 serial data.
• | The DTC will clear when 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 250 malfunction-free ignition cycles have occurred. |
The following are conditions that may cause the malfunction:
• | A short to ground or voltage in the ROS circuit |
• | High or low resistance in the ROS circuit |
• | Improper ROS installed on vehicle |
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis, causing a part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .
The numbers below refer to the step numbers on the diagnostic table.
This step tests the ROS signal and ROS voltage circuits for an open or high resistance.
This step tests between the ROS signal and ROS voltage circuits for continuity.
This step tests the ROS signal circuit for a short to voltage.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the scan tool indicate that DTC B3856, or B3857 is current? | Go to Step 10 | Go to Step 3 |
3 |
Does the connector exhibit any signs of damage or corrosion? | Go to Step 4 | Go to Step 5 |
4 |
Did you complete the repair? | Go to Step 11 | -- |
5 |
Does the connector exhibit any signs of damage or corrosion? | Go to Step 6 | Go to Step 7 |
6 |
Did you complete the repair? | Go to Step 11 | -- |
If DTC B3855 is current, test both the ROS signal and ROS voltage circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Step 8 | |
Test for continuity between the ROS signal circuit and the ROS voltage circuit on the ROS connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Step 9 | |
Did you find and correct the condition? | Go to Step 11 | Go to Step 10 | |
10 |
Did you complete the replacement? | Go to Step 11 | -- |
11 |
Does the DTC reset? | Go to Step 12 | System OK |
12 |
Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |