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

Circuit Description

SIR Side Impact Sensor (SIS) adopts one way 2-lined circuit. The side impact sensor modulates the interface current, sends the ID number, operation status and deployment command to the SIR SDM. The SDM provides the side impact sensor with power and ground. With ignition ON, the side impact sensor detects the power provided by the SDM for the first time, it will conduct internal diagnosis and send ID to the SDM as response. If the responsive time is less than 5 seconds, the SDM will take it as valid number. The side impact sensor sends the status messages continuously to the SDM, which in turn determines if the side impact sensor circuit is in trouble or not. When fault is detected, the SDM will reset the side impact sensor power through disconnecting and reconnecting. If the fault still exists, the SDM will set a DTC.

DTC Descriptor

The diagnostic procedure supports the following DTC:

DTC B0085 Left Front - Driver Side Impact Sensor

The vehicle has DTCs including the DTC symptoms. Refer to DTC Symptom Description for DTC information.

DTC Symptom

DTC Symptom Descriptor

01

Short to battery

02

Short to ground

04

Open circuit

39

Internal electronic fault

71

Invalid serial data received

0F

Side impact sensor unstable

3A

Component installed incorrectly

Conditions for Running the DTC

Ignition 1 voltage is within normal operating range.

Conditions for Setting the DTC

All the following conditions last for 2.5 seconds:

B0085 01

    • Side impact sensor is short to voltage.
    • The SDM fails to receive message from the side impact sensor for more than 375 milliseconds.

B0085 02

    • Side impact sensor is short to ground.
    • Side impact sensor current is more than 23 mA for more than 5 milliseconds.

B0085 04

Side impact sensor circuit is open.

B0085 39

    • The SDM receives NOK message from the side impact sensor.
    • The SDM fails to receive message.

B0085 71

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

B0085 0F

The SDM receives unstable message from the side impact sensor.

B0085 3A

    • The SDM receives ID message from side impact sensor, however, the ID does not match the ID information in the SDM memory.
    • The SDM resets the side impact sensor twice and still fails to detect the correct ID information.

Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON via GMLAN serial data communications.

Conditions for Clearing the MIL/DTC
    • When conditions for the DTC to set no longer exist, use CLEAR DTC function of the scan tool to clear the DTC.
    • After 255 consecutive warm-up cycles without failure, the DTC will be cleared.

Diagnostic Aids

The following conditions may cause the fault:

    • Side impact sensor circuit is open
    • Side impact sensor is short to voltage or to ground.
    • Side impact sensor has high or low resistance.
    • The side impact sensor installed in the vehicle is not correct
    • Side impact sensor internal fault

Thoroughly inspect the wiring and connectors. Failure to do so may result in error of diagnosis and the trouble may occur again even when you replace the parts. If there is intermittent conditions, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

The following numbers are corresponding to the steps in the diagnostic table.

  1. This step tests if the side impact sensor signal circuit and voltage circuit is open or has high resistance.

    2.

  2. This step tests the continuity of the side impact sensor signal circuit and voltage circuit.

    3.

  3. This step tests if the side impact sensor signal circuit and voltage circuit is short to voltage.

Step

Action

Yes

No

Schematic for Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Have you conducted Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Important: J-45289 CANdi Module must be used together with the scan tool.

  1. Install the scan tool in order to display the SIR DTCs.
  2. Engine off, ignition on.

Does the scan tool indicate DTC  B0085 as current trouble code?

Go to Step 3

Go to Step 13

3
  1. Turn the ignition switch to OFF position.
  2. If DTC B0085 is set as the current DTC, disconnect the left front SIR SIS connector. Refer to Inflatable Restraint Side Impact Sensor Replacement .
  3. Check if the component or harness of the connector is damaged or corrosive. Refer to Testing for Intermittent Conditions and Poor Connections .

Is there damage or corrosion in the connectors?

Go to Step 4

Go to Step 5

4
  1. Replace the side impact sensor if the component of the side impact sensor connector is damaged. Refer to Inflatable Restraint Side Impact Sensor Replacement .
  2. If the side impact sensor connector harness is damaged, replace the harness. Refer to Connector Repairs .

Is the trouble corrected?

Go to Step 11

--

5
  1. Turn the ignition switch to OFF position.
  2. Disconnect the SIR system sensing and diagnostic module (SDM) connector. Refer to Control Module References for replacement, set up, and programming.
  3. Check if the component or harness of the SDM connector is damaged or corrosive. Refer to Testing for Intermittent Conditions and Poor Connections for replacement, set up, and programming.

Is there damage or corrosion in the connectors?

Go to Step 6

Go to Step 7

6
  1. Replace the SDM if the component of the SDM connector is damaged. Refer to Control Module References for replacement, set up, and programming.
  2. If the SDM connector harness is damaged, replace the harness. Refer to Connector Repairs .

Is the trouble corrected?

Go to Step 11

--

7

  1. Disconnect the left front side impact sensor connector.
  2. Test if the signal circuit and voltage circuit between SDM connector and side impact sensor connector is open or has high resistance. Refer to Circuit Testing .

Do you find and correct the condition?

Go to Step 11

Go to Step 8

8

Test the continuity between the SDM connector side impact sensor signal circuit and voltage circuit. Refer to Circuit Testing .

Do you find and correct the condition?

Go to Step 11

Go to Step 9

9

  1. Engine off, ignition on.
  2. Test if the side impact sensor signal circuit and voltage circuit is short to voltage. Refer to Circuit Testing .

Do you find and correct the condition?

Go to Step 11

Go to Step 10

10
  1. Turn the ignition switch to OFF position.
  2. Replace the left front side impact sensor. Refer to Driver or Passenger Seat Side Inflatable Restraint Module Replacement .

Have you finished the replacement?

Go to Step 11

--

11
  1. Reconnect all SIR components.
  2. Clear away all DTCs with scan tool.
  3. Operate the vehicle under conditions when DTC runs as specified in supporting documents.

Does the DTC set again?

Go to Step 12

System OK

12
  1. Turn the ignition switch to OFF position.
  2. Replace the SDM module. Refer to Control Module References for replacement, set up, and programming.

Have you finished the replacement?

Go to Step 13

--

13
  1. Engine off, ignition on.
  2. Clear away all DTCs with scan tool.
  3. Operate the vehicle under conditions when DTC runs as specified in supporting documents.

Does the DTC set again?

Go to Step 2

System OK