For 1990-2009 cars

### 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.

Upon passing these tests, the ignition and deployment loop voltages are measured to ensure that these voltages are within the normal ranges. The SDM monitors the voltages at the driver low and the passenger low to detect shorts to ground or voltage in the deployment loops.

The SDM tests the wiring connection to extra devices, such as the side impact sensor, by letting an infinitesimal current flow through the internal circuit to verify the resistance. If the voltage is out of range, the SDM is unable to test the air bag system properly.

In the case of DTC B1103, test the battery and if necessary replace the battery with a new one. Erase the DTC using the scan tool.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1329 Front End Sensor 1 Invalid Serial Data Received

### Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

The early crash sensor - driver (LH) is defective or the air bag wiring harness is damaged.

### Action Taken When the DTC Sets

The SDM commands the AIR BAG indicator ON.

### Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Step | Action | Value(s) | 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. Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views
1 | Did you perform a Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn the ignition switch to OFF.
2. Wait 60 seconds for the sensing and diagnostic module (SDM) charger to discharge.

Is the SDM charger discharged?

--

Go to Step 3

--

3 | Visually inspect for damage to the early crash sensor - driver (LH) wiring. Is the early crash sensor - driver (LH) wiring damaged? | -- | Go to Step 4 | Go to Step 5
4 | Replace the air bag wiring. Did you complete the replacement? | -- | Go to Step 8 | --
5 |

1. Disconnect the SDM connector.
2. Disconnect the early crash sensor - driver (LH) connector.
3. Test the resistance between the terminal 74, 75 of the SDM and the terminal 2, 1 of the early crash sensor - driver (LH) .

Are the resistances approximately equal to the indicated value?

0 ohms

Go to Step 6

Go to Step 4

6 | Test the resistance between the terminal 74 and 75 of the SDM connector. Is the resistance equal to the indicated value? | ∞ | Go to Step 7 | Go to Step 4
7 | Replace the early crash sensor - driver (LH). Did you complete the replacement? | -- | Go to Step 8 | --
8 |

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

Does the DTC reset?

--

Go to Step 9

System OK

9 | Verify the part number of the early crash sensor - driver (LH). Is the part number correct for the vehicle? | -- | Go to Step 2 | Go to Step 7