B0101

CIRCUIT DESCRIPTION
The inflatable restraint front end sensor also known as the Electronic Frontal Sensor (EFS) utilizes a unidirectional 2-wire circuit. The EFS 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 EFS. When the ignition is turned on and input power from the SDM is first detected, the EFS 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 EFS continually communicates status messages to the SDM, which determines if a fault is present in the EFS circuit. When a fault is detected, the SDM resets the EFS twice 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.

CONDITIONS FOR SETTING THE DTC
- DTC B0100 for the EFS will set when one of the following conditions occur:
- A valid ID message is not received within 5 seconds of the EFS being powered up.
- Status message is not received.
- The SDM has reset the EFS twice without detecting a valid ID message.
- DTC B0101 for the EFS will set when the SDM has received a NOK message from the EFS.
- DTC B0102 for the EFS will set when one of the following conditions occur:
- The SDM has received an ID message from the EFS which does not match the ID stored in the SDM memory.
- The SDM has reset the EFS twice without detecting a correct ID message.

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 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 EFS circuit
- High or low resistance in the EFS circuit
- Improper EFS 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 and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-2:

Steps 3-5:

Steps 6-10:

Steps 11-13:

The numbers below refer to the step numbers on the diagnostic table.
7. This step tests the EFS signal and EFS voltage circuits for an open or high resistance.
8. This step tests between the EFS signal and EFS voltage circuits for continuity.
9. This step tests the EFS signal and EFS voltage circuits for a short to voltage.