GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 DTC 🢒 DTC B0085

Circuit 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 diagnostic trouble code (DTC).

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B0085 LF/Driver Side Impact Sensor

This vehicle has DTCs which include DTC symptoms. For more information on DTC symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC Symptom

DTC Symptom Descriptor

01

Short To Battery

02

Short To Ground

04

Open Circuit

39

Internal Electronic Failure

71

Invalid Serial Data Received

0F

Erratic Side Impact Sensor

3A

Incorrect Component Installed

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC

All of the following conditions exist for 2.5 seconds:

B0085 01

    • The SIS has been shorted to voltage.
    • The SDM has not received a message from the SIS for more than 375 milliseconds.

B0085 02

    • The SIS has been shorted to ground.
    • The SIS current has been above 23 mA for longer than 5 milliseconds.

B0085 04

The SIS circuit is open.

B0085 39

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

B0085 71

The SDM has received invalid serial data from the SIS.

B0085 0F

The SDM has received erratic messages from the SIS.

B0085 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 ON the AIR BAG warning lamp via GMLAN serial data.

Conditions for Clearing the MIL/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 255 malfunction free ignition cycles have occurred.

Diagnostic Aids

The following are conditions that may cause the malfunction:

    • An open in the SIS circuit
    • A short to ground or voltage in the SIS circuit
    • High or low resistance in the SIS circuit
    • Improper SIS installed on vehicle
    • An internal failure in the SIS

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, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests the SIS signal and SIS voltage circuits for an open or high resistance.

    2.

  2. This step tests between the SIS signal and SIS voltage circuits for continuity.

    3.

  3. This step tests the SIS signal and SIS voltage circuits for a short to voltage.

Step

Action

Yes

No

Schematic Reference: SIR Schematics

Connector End View Reference: SIR Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

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

  1. Install a scan tool, request the SIR DTC display.
  2. Turn ON the ignition, with the engine OFF.

Does the scan tool indicate that DTC B0085 is current?

Go to Step 3

Go to Step 13

3

  1. Turn OFF the ignition.
  2. If DTC B0085 is current, disconnect the inflatable restraint side impact sensor (SIS) - LF connector. Refer to Inflatable Restraint Side Impact Sensor Replacement .
  3. Inspect both the component and harness sides of the connector for damage or corrosion. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Does the connector exhibit any signs of damage or corrosion?

Go to Step 4

Go to Step 5

4
  1. If the component side of the SIS connector is damaged, the SIS must be replaced. Refer to Inflatable Restraint Side Impact Sensor Replacement .
  2. If the harness side of the SIS connector is damaged, replace the harness side of the connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

5
  1. Turn OFF the ignition.
  2. Disconnect the inflatable restraint sensing and diagnostic module (SDM) connector. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
  3. Inspect both the component and harness sides of the SDM connector for damage or corrosion. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Does the connector exhibit any signs of damage or corrosion?

Go to Step 6

Go to Step 7

6
  1. If the component side of the SDM connector is damaged, the SDM must be replaced. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
  2. If the harness side of the SDM connector is damaged, replace the harness side of the connector. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

7

  1. Disconnect the SIS - LF connector.
  2. Test both the SIS signal and SIS voltage circuits for an open or high resistance between the SDM connector and the SIS connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 8

8

Test for continuity between the SIS signal circuit and the SIS voltage circuit on the SDM connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

9

  1. Turn ON the ignition, with the engine OFF.
  2. Test both SIS signal and SIS voltage circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

10
  1. Turn OFF the ignition.
  2. Replace the SIS - LF. Refer to Inflatable Restraint Side Impact Sensor Replacement .

Did you complete the replacement?

Go to Step 11

--

11
  1. Reconnect all SIR components.
  2. Use the scan tool in order to Clear the DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the text.

Does the DTC reset?

Go to Step 12

System OK

12
  1. Turn OFF the ignition.
  2. Replace the SDM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 13

--

13
  1. Turn ON the ignition, with the engine OFF
  2. Use the scan tool in order to Clear the DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the text.

Does the DTC reset?

Go to Step 2

System OK