GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 GTO 🢒 Restraints 🢒 SIR 🢒 DTC B0012

Circuit Description

The air bag sensing and diagnostic module (SDM) sends serial data along the tertiary serial data bus, circuit 774, to the body control module (BCM) and then on to the instrument cluster on the secondary serial data bus, circuit 1061. This is read by the instrument cluster, which displays the status of the SDM on the multifunction display (MFD) and cluster indicator. DTC 12 will set if there is no SDM data message on the bus for more than 10 seconds. The DTC is reset within 10 seconds of the arrival of a SDM data message on the bus. The DTC is logged as a History DTC.

Diagnostic Aids

By manipulating the harnesses at the various connectors it is often possible to isolate the cause of the circuit interruption. This harness can then be removed and repaired. Inspect for any damage to the harness which could cause an intermittent open or short to ground or backed out terminals at the instrument cluster connectors, broken connector locks, improperly formed or damaged terminals. The multimeter allows continuity of the wiring harness circuit 774 to be checked. If the fault cannot be found in the harness then the fault may lie in the SDM or the BCM. Refer to Diagnostic Starting Point - Computer/Integrating Systems for further diagnosis.

DTC 12 - NO SERIAL DATA FROM SDM

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. With the scan tool, observe the Supplemental Inflatable Restraint Data display.

Does the Tech 2 display Engine information?

--

Go to Step 3

Go to Scan Tool Does Not Communicate with UART Device

3
  1. Disable the Occupant Protection System. Refer to SIR Disabling and Enabling in SIR.
  2. Disconnect the body control module (BCM) connector 2.
  3. Disconnect the sensing and diagnostic module (SDM) connector.
  4. Check continuity of the tertiary universal asynchronous receiver transmitter (UART) serial data circuit between the BCM and the SDM. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 4

Go to Step 6

4
  1. Remove the instrument cluster.
  2. Check the Secondary UART Serial Data circuit for continuity between the BCM and the instrument panel (I/P). Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 5

Go to Step 7

5
  1. Remove the instrument cluster.
  2. Check the Secondary UART Serial Data circuit for continuity between the BCM and the I/P. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

--

Go to Step 8

Go to Step 7

6

Repair the open or high resistance in the Secondary UART Serial Data circuit between the BCM and the SDM. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 8

--

7

Repair the open or high resistance in the Secondary UART Serial Data circuit between the powertrain control module (PCM) and the powertrain interface module (PIM). Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 8

--

8
  1. Use the scan tool in order to clear the DTCs.
  2. 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