Circuit Description
The inflatable restraint side impact sensor (SIS) utilizes a unidirectional 2-wire circuit. The SIS modulates current on the interface to send ID, State of Health, and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). The SDM serves as a power source and a ground for the SIS. When the ignition is turned on and input power from the SDM is first detected, the SIS responds by performing internal diagnostics and sending an ID to the SDM. The SDM considers the ID to be valid if the response time is less than 5 seconds. The SIS continually communicates status messages to the SDM, which determines if a fault is present in the SIS circuit. When a fault is detected, the SDM may reset the SIS up to two times by removing and reapplying power to it. If the fault is still present, the SDM will set a diagnostic trouble code (DTC).
Conditions for Running the DTC
Ignition 1 Voltage is within the normal operating voltage range of 9-16 volts.
Conditions for Setting the DTC
| • | DTC B0077 will set when one of the following conditions occur: |
| - | A valid ID message is not received within 5 seconds of the SIS being powered up. |
| - | A status message is not received. |
| - | The SDM has reset the SIS twice without detecting a valid ID message. |
| • | DTC B0079 will set when one of the following conditions occur: |
| - | The SDM has received an ID message from the SIS which does not match the ID stored in the SDM memory. |
| - | The SDM has reset the SIS twice without detecting the correct ID message. |
| • | DTC B0080 will set when the SDM has received a NOK message from the SIS. |
Action Taken When the DTC Sets
The SDM commands ON the AIR BAG warning lamp via Class 2 serial data.
Conditions for Clearing the DTC
| • | The DTC will clear when the condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used. |
| • | A history DTC will clear once 255 malfunction free ignition cycles have occurred. |
Diagnostic Aids
The following are conditions that may cause the malfunction:
| • | A short to ground or voltage in the SIS circuit |
| • | High or low resistance in the SIS circuit |
| • | Improper SIS installed on vehicle |
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis, causing a part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests the SIS signal and SIS voltage circuits for an open or high resistance.
-
Tests between the SIS signal and SIS voltage circuits for continuity.
-
Tests the SIS signal and SIS voltage circuits for a short to voltage.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: SIR Schematics | |||
1 | Did you perform the Diagnostic System Check - SIR? | Go to Step 2 | |
2 |
Does the scan tool indicate that DTC B0079, or B0080 is current? | Go to Step 10 | Go to Step 3 |
3 |
Does the connector exhibit any signs of damage or corrosion? | Go to Step 4 | Go to Step 5 |
4 |
Did you complete the repair? | Go to Step 11 | -- |
5 |
Does the connector exhibit any signs of damage or corrosion? | Go to Step 6 | Go to Step 7 |
6 |
Did you complete the repair? | Go to Step 11 | -- |
Did you find and correct the condition? | Go to Step 11 | Go to Step 8 | |
Test for continuity between the SIS signal circuit and the SIS voltage circuit on the SDM connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 | |
Did you find and correct the condition? | Go to Step 11 | Go to Step 10 | |
10 |
Did you complete the replacement? | Go to Step 11 | -- |
11 |
Does the DTC reset? | Go to Step 12 | System OK |
12 |
Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
