Circuit Description
The inflatable restraint front end sensor utilizes a unidirectional 2-wire circuit. The front end sensor 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 front end sensor. When the ignition is turned ON and input power from the SDM is first detected, the front end sensor 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 front end sensor continually communicates status messages to the SDM, which determines if a fault is present in the front end sensor circuit. When a fault is detected, the SDM resets the front end sensor twice by removing and reapplying power. If the fault is still present, the SDM will set a DTC.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0077 Left Side Impact Sensor (SIS) Malfunction |
| • | DTC B0079 Incorrect Left Side Impact Sensor (SIS) Installed |
| • | DTC B0080 Discard Left Side Impact Sensor (SIS) |
Conditions for Running the DTC
Ignition 1 voltage is within the normal operating voltage range.
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 front end sensor being powered up. |
| - | Status message is not received. |
| - | The SDM has failed twice to reset the front end sensor. |
| • | DTC B0079 will set when one of the following conditions occur: |
| - | The SDM has received an ID message from the front end sensor which does not match the ID stored in the SDM memory. |
| - | When 2 front end sensor resets are attempted without the correct identification being detected by the SDM. |
| • | DTC B0080 will set when the SDM has received a NOK (Not OK) message from the front end sensor. |
Action Taken When the DTC Sets
| • | The SDM commands the AIR BAG indicator ON via class 2 serial data. |
| • | The SDM attempts to reset the front end sensor. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | You issue a scan tool CLEAR DTCs command. |
| • | A history DTC will clear once 255 malfunction-free ignition cycles have occurred. |
Diagnostic Aids
The following can cause an intermittent condition:
| • | A short between the front end sensor signal and low reference circuits |
| • | High or low resistance in the front end sensor signal and low reference circuits |
| • | Inspect the front end sensor signal and low reference circuits carefully for cutting and/or chafing. |
| • | Verify that the correct front end sensor is installed in the vehicle. |
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:
-
This step tests the communication status of the front end sensor.
-
This step tests for a short to ground, a high resistance, or an open in the front end sensor signal circuit.
-
This step tests for a short to ground, a high resistance, or an open in the front end sensor low reference circuit.
-
This step tests for a short to voltage in the front end sensor signal and low reference circuits.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: SIR Schematics Connector End View Reference: SIR Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool indicate that either DTC B0079, or B0080 is current? | Go to Step 12 | Go to Step 3 | |
3 |
Does the front end sensor terminals or harness connector exhibit any signs of damage or corrosion? | Go to Step 4 | Go to Step 5 |
4 |
Did you complete the replacement? | Go to Step 13 | -- |
5 |
Did you find and correct the condition? | Go to Step 13 | Go to Step 6 |
Test the front end sensor signal circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 7 | |
Test the front end sensor low reference circuit for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 8 | |
Did you find and correct the condition? | Go to Step 13 | Go to Step 9 | |
9 | Replace the front end sensor. Refer to Inflatable Restraint Front End Sensor Replacement . Did you complete the replacement? | Go to Step 10 | -- |
10 |
Does the DTC reset? | Go to Step 11 | System OK |
11 | Replace the SDM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the front end sensor. Refer to Inflatable Restraint Front End Sensor Replacement . Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
