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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Tahoe - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC B0040 LF/Driver Side Deployment Loop Resistance Low

Object Number: 612828 Size: SF
SIR Components
SIR Schematics Utilities
SIR Caution
Handling ESD Sensitive Parts Notice
SIR Schematic Icons

Circuit Description

When you first turn the ignition switch to the RUN position, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM then performs the following continuous diagnostic tests on the deployment loops:

    • Deployment loop voltage out of range test
    • Deployment loop resistance measurement test

If the voltage out of range test detects a short to voltage condition, the resistance measurement test for that deployment loop will not be performed.

Conditions for Running the DTC
    • Ignition 1 voltage is within the normal operating voltage range.
    • Driver side deployment loop is not open.
    • Driver side deployment loop is not shorted to voltage.
    • Driver side deployment loop is not shorted to ground.

Conditions for Setting the DTC

The SDM detects the resistance between the driver side high and low side of the deployment loop is less than 1.3 ohms for 500 milliseconds.

Action Taken When the DTC Sets
    • The SDM commands ON the AIR BAG warning lamp via Class 2 serial data.
    • The SDM also sets this DTC as current after an accident. The SDM will write the status of this DTC to the "crash log" area of the EEPROM for retrieval.

Conditions for Clearing the DTC
    • Driver side deployment loop resistance is 1.3 ohms or greater for 500 milliseconds.
    • You issue a scan tool CLEAR CODES command.
    • A history DTC will clear once 255 malfunction free ignition cycles have occurred.

When the SDM detects that no DTCs are present, the SDM commands the AIR BAG warning lamp OFF.

Diagnostic Aids

The following can cause an intermittent condition:

    • A short between the driver side high and the driver side low circuits.
    • A malfunctioning shorting bar on the inflatable restraint side impact module 2-way harness connector.
    • Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step inspects the LF inflatable restraint side impact module in-line connector.

    2.

  2. Tests for a malfunctioning LF inflatable restraint side impact module.

    3.

  3. Tests for a short between the driver side high and low deployment circuits or if there is a malfunctioning SDM.

Step

Action

Value(s)

Yes

No

1

Did you perform the SIR Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

  1. Turn OFF the ignition.
  2. Disconnect the LF inflatable restraint side impact module in-line connector located under the seat.
  3. Inspect both wiring harness in-line connectors for any of the following conditions:
    4. • Corrosion
    •  Terminal damage
    • Poor connections/terminal tension

Do the connectors exhibit any signs of corrosion, terminal damage, or poor connections?

--

Go to Step 3

Go to Step 4

3
  1. Repair or replace the wiring harness side of the in-line connector. Refer to Connector Repairs in Wiring Systems.
  2. If the side impact module wiring harness connector exhibits any of the above conditions, replace the side impact module wiring harness.

Did you complete the replacement?

--

Go to Step 10

--

4
  1. Reconnect the LF inflatable restraint side impact module in-line connector.
  2. Verify that the connector position assurance (CPA) is properly installed.
  3. Turn ON the ignition, with the engine OFF.
  4. Use the scan tool to request the SIR DTC display.

Does the scan tool indicate that DTC B0040 is current?

--

Go to Step 5

Go to Diagnostic Aids

5

  1. Turn OFF the ignition.
  2. Disconnect the LF inflatable restraint side impact module in-line connector.
  3. Install theJ 38715-A SIR Load Tool to the wiring harness side of the in-line connector. Use appropriate connector adaptors where necessary.
  4. Turn ON the ignition, with the engine OFF.
  5. Use the scan tool to request the SIR DTC display.

Does the scan tool indicate that DTC B0040 is current?

--

Go to Step 6

Go to Step 9

6

  1. Turn OFF the ignition.
  2. Remove theJ 38715-A SIR Load Tool.
  3. Disconnect the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .
  4. UsingJ 39200 DMM measure the resistance between the driver side high circuit and driver side low circuit at the inflatable restraint sensing and diagnostic module (SDM) connector. Refer to Circuit Testing in Wiring Systems.

Does the resistance measure less than the specified value?

OL

Go to Step 7

Go to Step 8

7

Locate and repair a short between the driver side high and driver side low deployment circuits. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 10

--

8

Replace the inflatable restraint sensing and diagnostic module (SDM). Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Did you complete the replacement?

--

Go to Step 10

--

9

Replace the LF inflatable restraint side impact module. Refer to Inflatable Restraint Front Seat Side Impact Inflator Module Replacement .

Did you complete the replacement?

--

Go to Step 10

--

10
  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