GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 STS 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B0085 or B0086

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B0085 00 : Left Front Side Impact Sensor No Additional Information

DTC B0085 39 : Left Front Side Impact Sensor Internal Electronic Failure

DTC B0085 0F : Left Front Side Impact Sensor Incorrect Component Installed

DTC B0085 3A : Left Front Side Impact Sensor Invalid Serial Data Received

DTC B0086 00 : Right Front Side Impact Sensor No Additional Information

DTC B0086 39 : Right Front Side Impact Sensor Internal Electronic Failure

DTC B0086 0F : Right Front Side Impact Sensor Incorrect Component Installed

DTC B0086 3A : Right Front Side Impact Sensor Invalid Serial Data Received

Circuit/System Description

The inflatable restraint side impact sensor (SIS) utilizes a unidirectional 2-wire circuit. The SIS modulates current on the interface to send ID, state of health, and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). The SDM serves as a power source and a ground for the SIS. When the ignition is turned ON and input power from the SDM is first detected, the SIS responds by performing internal diagnostics and sending an ID to the SDM. The SDM considers the ID to be valid if the response time is less than 5 seconds. The SIS continually communicates status messages to the SDM, which determines if a fault is present in the SIS circuit. When a fault is detected, the SDM resets the SIS twice by removing and reapplying power to it. If the fault is still present, the SDM will set a DTC.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

B0085 00 or B0086 00

    • The SIS has been shorted to voltage, open or shorted to ground.
    • The SIS current has been above 23 mA for longer than 5 milliseconds.
    • The SDM has not received a message from the SIS for more than 375 milliseconds.

B0085 39 or B0086 39

    • The SDM has received a NOK message from the SIS.
    • The SDM has not received a message.

B0085 0F or B0086 0F

The SDM has received erratic messages from the SIS.

B0085 3A or B0086 3A

    • The SDM has received an ID message from the SIS which does not match the ID stored in the SDM memory.
    • The SDM has reset the SIS twice without detecting the correct ID message.

Action Taken When the DTC Sets
    • The SDM commands the AIR BAG indicator ON via serial data communications.
    • The side SIR System is disabled and no side deployments are allowed. Frontal deployments and rollover detection are still enabled.

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

SIR Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Testing

    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 front end sensor
       • The SDM module
       • The front end sensor wiring harness connector
       • The SDM wiring harness connector

  1. Ignition OFF, disconnect the harness connector at the applicable front end sensor and the harness connector at the SDM.
  2. Test for infinite resistance between the applicable impact sensor signal circuit terminal B and ground.
    3. ⇒If less than the specified value, test the circuit for a short to ground.
  3. Ignition ON, test for less than 1 volt between the applicable impact sensor signal circuit terminal B and ground.
    4. ⇒If greater than the specified range, test the circuit for a short to voltage.
  4. Ignition ON, test for less than 1 volt between the applicable impact sensor low reference circuit terminal A and ground.
    5. ⇒If greater than the specified range, test the circuit for a short to voltage.
  5. Test for less then 1 ohm of resistance between the applicable impact sensor low reference circuit and the SDM.
    6. ⇒If greater than the specified range, test the circuit for an open/high resistance. If the circuits test normal, replace the applicable front end sensor.
  6. Test for less then 1 ohm of resistance between the applicable impact sensor signal circuit and the SDM.
    7. ⇒If greater than the specified range, test the circuit for an open/high resistance. If the circuits test normal, replace the applicable front end sensor.
  7. If all circuits test normal, replace the applicable impact sensor.
  8. With a scan tool, clear DTCs.
  9. Verify DTC B0083 or B0084 is not set.
    10. ⇒If DTC is set, replace the SDM.

Repair Instructions
    •  Inflatable Restraint Side Impact Sensor Replacement
    •  SIR/SRS Wiring Repairs
    •  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 B0085 or B0086 was current, replace the SDM.