GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Aveo 🢒 DTC 🢒 DTC 025

Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform a turn-on test to diagnose critical malfunctions within the SDM itself.

The test ignition and deployment loop voltages are measured to ensure that they are within their normal voltage ranges. The SDM monitors the voltages at the driver low and the passenger low to detect shorts to ground or voltage in the deploy loops.

The SDM inspects the wiring connection to the passenger air bag module by letting the infinitesimal current flow through the internal circuit and verify the resistance. If the warning lamp operates properly ON and OFF, the SDM measures the voltage continuously from the warning lamp terminal.

Conditions for Setting the DTC

The warning lamp does not blink properly ON and OFF.

Diagnostic Aids

When the ignition switch is turned ON, the warning lamp blinks 7 times during 7 seconds.

If the warning lamp stays ON or blinks a second after the normal blinking, 7 times during 7 seconds, then it is regarded as a defect, old or current. Please inspect the defect with a scan tool.

Step

Action

Values

Yes

No

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.

 

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

Turn the ignition ON.

Is the warning lamp constantly ON?

--

Go to Step 3

Go to Step 10

3

Make sure the sensing and diagnostic module (SDM) connector is attached correctly.

Does the warning lamp turn OFF?

--

Go to Diagnostic System Check - SIR

Go to Step 4

4
  1. Inspect for indications of a diagnostic trouble code (DTC) other than code 025.
  2. Go to the appropriate DTC charts and repair each additional problem.
  3. Perform the Diagnostic System Check - SIR .

Does the scan tool still indicate the DTC 025?

--

Go to Step 5

System OK

5

Inspect for a short to ground between the SDM and the warning lamp using the following method:

  1. Turn the ignition OFF.
  2. Disconnect the connector C214.
  3. Connect 1 ohmmeter lead to ground.
  4. Touch the other ohmmeter lead to the terminal 3 of the connector C214 on the instrument harness side.

Does the ohmmeter indicate the specified value?

∞

Go to Step 7

Go to Step 6

6

Repair the short to ground in the instrument harness.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

7
  1. The connector C214 remains disconnected.
  2. One lead of the ohmmeter remains connected to ground.
  3. Move the ohmmeter lead at the connector C214 to the SDM side of the connector.

Does the ohmmeter indicate the specified value?

∞

Go to Step 8

Go to Step 9

8

Replace the SDM.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

9
  1. Disconnect the negative battery cable.
  2. Replace the SIR wiring harness.
  3. Perform the Diagnostic System Check - SIR .

Is DTC 025 still shown?

--

Go to Step 6

System OK

10

Inspect the fuse F4.

Is fuse F4 open?

--

Go to Step 11

Go to Step 12

11
  1. With the connector C214 temporarily disconnected, inspect for a short to ground between the fuse F4 and the warning lamp.
  2. Make a repair, if needed.
  3. Replace fuse F4.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

12
  1. Turn the ignition ON.
  2. Using a multimeter, measure the voltage at fuse F4.

Does the multimeter show the specified value?

11-14 V

Go to Step 14

Go to Step 13

13

Repair the open power supply circuit for the fuse F4.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

14
  1. Disconnect the connector C214.
  2. Turn the ignition ON.
  3. Using a multimeter, measure the voltage on the instrument harness side of the terminal 1 of the connector C214.

Does the multimeter show the specified value?

11-14 V

Go to Step 16

Go to Step 15

15
  1. Inspect the warning lamp bulb.
  2. Replace the warning lamp bulb, if needed.
  3. If the bulb is good, repair the open circuit between the fuse F4 and the terminal 1 of the connector C214.

Is the repair complete?

--

Go to Diagnostic System Check - SIR

--

16
  1. Disconnect the negative battery terminal.
  2. Wait at least 1 minute before proceeding.
  3. Replace the SIR wiring harness.

Is the repair complete?

--

System OK

--