B3857

DTC B3857

CIRCUIT 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).

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC B3855 Rollover Sensor Performance
- DTC B3856 Discard Rollover Sensor
- DTC B3857 Incorrect Rollover Sensor Installed

CONDITIONS FOR RUNNING THE DTC
Ignition 1 voltage is within the normal operating voltage range of 9-16 volts.

CONDITIONS FOR SETTING THE DTC
- 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.

ACTION TAKEN WHEN THE DTC SETS
The SDM commands ON the AIR BAG warning lamp via class 2 serial data.

CONDITIONS FOR CLEARING THE DTC
- 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.

DIAGNOSTIC AIDS
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,

TEST DESCRIPTION

Step 1 - Step 11:

Step 12 - Step 13:

The numbers below refer to the step numbers on the diagnostic table.
7. This step tests the ROS signal and ROS voltage circuits for an open or high resistance
8. This step tests between the ROS signal and ROS voltage circuits for continuity
9. This step tests the ROS signal circuit for a short to voltage