GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC B0036

Circuit Description

The inflatable restraint sensing and diagnostic module (SDM) monitors the inflatable restraint front end discriminating sensor circuit for front impact detection. The SDM processes the signal provided by the front end discriminating sensor to further support deployment of the air bags. The front end discriminating sensor is an input only to the SDM and does not directly cause air bag deployment. When the ignition is turned ON, the SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a DTC will be stored.

Conditions for Running the DTC

Ignition 1 voltage is within the normal operating voltage range.

Conditions for Setting the DTC

The SDM detects the voltage at the front end discriminating sensor signal is greater than 3.65 volts for 500 milliseconds.

Action Taken When the DTC Sets

The SDM commands ON the AIR BAG indicator via Class 2 serial data.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • You issue a scan tool CLEAR DTCs command.
    • A history DTC will clear once 255 malfunction free ignition cycles have occurred.

Diagnostic Aids

A broken or chafed wire in the front end discriminating sensor circuit may cause an intermittent condition to occur. 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. Tests for a malfunctioning front end discriminating sensor.

    2.

  2. Tests for an open or high resistance in the front end discriminating sensor signal circuit.

    3.

  3. Tests for an open or high resistance in the front end discriminating sensor reference low circuit.

    4.

  4. Tests for a short to voltage in the front end discriminating sensor signal circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: SIR Schematics

1

Did you perform the Diagnostic System Check - SIR?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2
  1. Turn OFF the ignition.
  2. Disconnect the front end discriminating sensor in-line connector. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .
  3. Inspect both halves of the connector for corrosion or damage. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 3

3
  1. Disconnect the front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .
  2. Inspect the connector for corrosion or damage. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 4

4
  1. Disconnect the SDM connector. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  2. Inspect the connector for corrosion or damage. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 5

5

  1. Disconnect the front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .
  2. Test the resistance between the front end discriminating sensor terminals. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure more than the specified value?

1050 ohms

Go to Step 9

Go to Step 6

6

Test the front end discriminating sensor signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the front end discriminating sensor reference low circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

8

  1. Disable the SIR system. Refer to Disabling the SIR System .
  2. Install the AIR BAG Fuse.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the front end discriminating sensor signal circuit 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 12

Go to Step 9

9

Replace the front end discriminating sensor. Refer to Inflatable Restraint Front End Discriminating Sensor Replacement .

Did you complete the replacement?

--

Go to Step 10

10
  1. Reconnect all SIR system 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 supporting text.

Does the DTC reset?

--

Go to Step 11

System OK

11

Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Reconnect all SIR system components.
  2. Verify that all components, connectors, and CPAs are properly mounted.
  3. Use the scan tool in order to clear the DTCs.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK