GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Vivant 🢒 Preface 🢒 Cautions and Notices 🢒 DTC 018

Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform tests to diagnose critical malfunctions within itself. Upon passing these tests, ignition and deployment loop voltages are measured to ensure that they are within their respective normal voltage ranges. The SDM monitors the voltages at the driver low, terminal A7, and the passenger low, terminal A8, to detect shorts to ground or voltage in the deployment loops.

Conditions for Setting the DTC
    • Ignition voltage is within a specified value.
    • Voltage at the passenger high is higher than 6 volts for 500 milliseconds.
    • Voltage at passenger high is less than 2 volts and the resistance of passenger deployment loop is less than 4.5 ohms for 500 milliseconds.

Action Taken When the DTC Sets
    • The SDM will turn on the AIRBAG indicator and set a DTC 18.
    • The SDM will disable the passenger deployment resistance test.

Conditions for Clearing the DTC
    • Voltage at the passenger high is less than 6 volts for 500 milliseconds.
    •  Voltage at passenger high is higher than or equal to 2 volts and the resistance of passenger deployment loop is less than 4.5 ohms for 500 milliseconds.
    • Turn OFF the ignition switch.
    • The scan tool CLEAR CODES command is received.

Diagnostic Aids

Carefully inspect the wires in the passenger loop for cutting or chafing.

Caution: Refer to Sensing and Diagnostic Module Voltage after Ignition is Turned Off Caution in the Preface section.

Caution: Refer to Sensing and Diagnostic Module Handling Caution in the Preface section.

Step

Action

Values

Yes

No

1

Perform the Diagnostic System Check - SIR.

Is the Diagnostic System Check - SIR complete?

--

Go to Step 2

Go to Diagnostic System Check - SIR

2

Visually inspect the wires to the passenger airbag, including the connector of the passenger airbag.

Is there any evidence of rubbing, damage, or chafing?

--

Go to Step 3

Go to Step 4

3
  1. Turn OFF the ignition and remove the key.
  2. Temporarily disconnect the passenger airbag, the yellow clock spring connector on the steering column and connector C221.
  3. Replace the damaged wiring, terminals, or harnesses.
  4. Replace the SDM. The arrow must be pointing to the front of the vehicle. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement .

Did you complete the repair?

--

Go to Diagnostic System Check - SIR

--

4
  1. Turn the ignition OFF.
  2. Disconnect the passenger airbag, the yellow clock spring connector on the steering column and connector C221.
  3. Disconnect the SDM.
  4. Using a digital multimeter, measure resistance at the SDM harness connector between terminal A3 and terminal A18, ground.

Refer to Diagnostic Illustration 6 in SIR Diagnostic Illustrations .

Is the resistance equal to the specified value?

∞

Go to Step 5

Go to Step 6

5
  1. Turn ON the ignition.
  2. Using a digital multimeter, measure voltage at the SDM harness connector between terminal A3 and terminal A18, ground.

Refer to Diagnostic Illustration 6 in SIR Diagnostic Illustrations .

Is the voltage below the specified value?

1.0 V

Go to Step 7

Go to Step 6

6
  1. Repair the short to ground between the passenger high circuit and ground/voltage.
  2. Replace the SDM. The arrow must be pointing to the front of the vehicle.

Did you complete the repair?

--

Go to Step 7

--

7
  1. Disconnect the SDM.
  2. Measure the resistance at the SDM connector between terminal A8 and terminal A18, ground.

Refer to Diagnostic Illustration 5 in SIR Diagnostic Illustrations .

Is the resistance equal to the specified value?

∞

Go to Step 8

Go to Step 10

8
  1. Turn ON the ignition.
  2. Using a digital multimeter to measure the voltage at the SDM connector terminal A8 and terminal A18, ground.

Refer to Diagnostic Illustration 7 in SIR Diagnostic Illustrations .

Is the voltage above the specified value?

1.0 V

Go to Step 10

Go to Step 9

9
  1. Repair the short to ground/voltage between the passenger low circuit and ground.
  2. Replace the SDM. The arrow must be pointing to the front of the vehicle.

Did you complete the repair?

--

Go to Diagnostic System Check - SIR

--

10
  1. Replace the passenger airbag. Refer to Inflatable Restraint Instrument Panel Module Replacement .
  2. Replace the SDM. The arrow must be pointing to the front of the vehicle.

Did you complete the repair?

--

Go to Diagnostic System Check - SIR

--