GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

DTC Descriptor

DTC B0085 01: LF Side Impact Sensor Short to Battery

DTC B0085 02: LF Side Impact Sensor Short to Ground

DTC B0085 0F: LF Side Impact Sensor Erratic Serial Data Received

DTC B0085 39: LF Side Impact Sensor Internal Electronic Failure

DTC B0085 3A: LF Side Impact Sensor Incorrect Component Installed

DTC B0085 71: LF Side Impact Sensor Invalid Serial Data Received

DTC B0086 01: RF Side Impact Sensor Short to Battery

DTC B0086 02: RF Side Impact Sensor Short to Ground

DTC B0086 0F: RF Side Impact Sensor Erratic Serial Data Received

DTC B0086 39: RF Side Impact Sensor Internal Electronic Failure

DTC B0086 3A: RF Side Impact Sensor Incorrect Component Installed

DTC B0086 71: RF Side Impact Sensor Invalid Serial Data Received

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

LF Side Impact Sensor High Signal

B0085 02

B0085 71

B0085 01

B0085 01

B0085 0F

LF Side Impact Sensor Low Reference

--

B0085 71

B0085 01

--

B0085 0F

RF Side Impact Sensor High Signal

B0086 02

B0086 71

B0086 01

B0086 01

B0086 0F

RF Side Impact Sensor Low Reference

--

B0086 71

B0086 01

--

B0086 0F

Circuit/System Description

The inflatable restraint side impact sensor utilizes a 2-wire circuit. The side impact sensor receives 25 volts from the inflatable restraint sensing and diagnostic module (SDM). The side impact sensor modulates the voltage in order to send ID, state of health, and deployment commands to the SDM. When the ignition is turned ON and input power from the SDM is first detected, the side impact sensor 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 side impact sensor continually communicates status messages to the SDM, which determines if a fault is present in the sensor circuit. When a fault is detected, the SDM may reset the side impact sensor up to 2 times by removing and reapplying power to it. If the fault is still present, DTC B0085 or B0086 and the appropriate symptom byte sets.

Conditions for Running the DTC

Ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

All of the following conditions exist for 2.5 seconds:

B0085 01 or B0086 01

    • The side impact sensor signal circuit voltage is greater than the expected value.
    • The SDM did not receive a message from the side impact sensor for more than 375 milliseconds

B0085 02 or B0086 02

    • The side impact sensor signal circuit is shorted to ground.
    • The side impact sensor current is greater than 23 mA for greater than 5 milliseconds.

B0085 0F or B0086 0F

The SDM received erratic messages from the side impact sensor.

B0085 39 or B0086 39

The SDM received a NOK message from the side impact sensor.

B0085 3A or B0086 3A

    • The SDM received an ID message from the side impact sensor that does not match the ID stored in the SDM memory.
    • The SDM has reset the side impact sensor twice without detecting the correct ID message.

B0085 71 or B0086 71

The SDM received invalid serial data from the side impact sensor.

Action Taken When the DTC Sets

    • The SDM requests the instrument panel cluster (IPC) to illuminate the AIR BAG indicator and display the message "Service Air Bag".
    • The SIR System is disabled and no deployments are allowed.

Conditions for Clearing the DTC

    • The condition for setting the DTC no longer exists.
    • A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

SIR Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

SIR System Description and Operation

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: Refer to SIR Service Precautions.

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 SDM and the appropriate side impact sensor.
  2. Ignition ON, test for less than 1-volt between the side impact sensor circuit terminals listed below and ground:
  3. • Side impact sensor low reference circuit terminal A and ground.
    • Side impact sensor signal circuit terminal B and ground.
  4. Test for infinite resistance between the side impact sensor voltage circuit terminal B and ground.
  5. If less than the specified value, test the voltage circuit for a short to ground.
  6. Test for less than 1 ohm between the side impact sensor circuit terminals listed below:
  7. • Right side impact sensor terminal A and SDM harness connector terminal 48
    • Right side impact sensor terminal B and SDM harness connector terminal 49.
    • Left side impact sensor terminal A and SDM harness connector terminal 47.
    • Left side impact sensor terminal B and SDM harness connector terminal 46.
    If greater than the specified range, test the circuit for an open/voltage resistance.
  8. If all circuits test normal, replace the appropriate side impact sensor.
  9. Reconnect all SIR components. Ignition ON, verify the DTC does not set as current.
  10. If the DTC resets as current, replace the SDM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Inflatable Restraint Side Impact Sensor Replacement
    •  SIR/SRS Wiring Repairs
    •  Control Module References for SDM replacement, setup, and programming