B3856

DTC B3855, B3856, or B3857

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3855
- Rollover Sensor Performance

DTC B3856
- Discard Rollover Sensor

DTC B3857
- Incorrect Rollover Sensor Installed

Diagnostic Fault Information






Circuit/System Description

The inflatable restraint vehicle rollover sensor utilizes battery power supply and a bidirectional interface circuit. The rollover sensor 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 rollover sensor responds by performing internal diagnostics and sending an ID to the SDM. The rollover sensor continually communicates status messages to the SDM, which determines if a fault is present in the rollover sensor circuit.

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 rollover sensor being powered up.
* A status message is not received.

B3856
* The SDM has received a NOK message from the rollover sensor.
* A ROS internal fault exists for a 127 ignition cycles.

B3857

When the SDM has received an ID message from the rollover sensor 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.
* A history DTC will clear once 250 malfunction-free ignition cycles have occurred.

Circuit/System Testing

1. Ignition ON, if B3856 or B3857 is current, replace the rollover sensor.
2. Ignition OFF, disconnect the harness connector at the rollover sensor.
3. Test for less than 1.0 ohm between the ground circuit terminal 6 and ground.

^ If greater than the specified range, test the ground circuit for an open/high resistance.

4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.

^ If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

5. Ignition OFF, disconnect the harness connector at the SDM.
6. Test for infinite resistance between the rollover sensor terminal 5 and the SDM serial data link terminal 35.

^ If less than the specified value, test the serial data link for a short to ground.

7. If all circuits test normal, replace the rollover sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Inflatable Restraint Vehicle Rollover Sensor Replacement