B0100

CIRCUIT DESCRIPTION
When the ignition is turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. Then, the SDM provides input power to the electronic frontal sensor (EFS Left), also known ai front end discriminating sensor. When the input power is detected, the EFS Left responds by performing internal diagnostics. After that, the EFS Left sends an ID message to the SDM. The SDM will consider this to be a valid ID if the response time is less than 5 seconds after the EFS Left is powered up. The EFS Left will continually communicate a status message to the SDM. The SDM can reset the EFS Left by removing and applying power to it.

CONDITIONS FOR RUNNING THE DTC
Ignition 1 voltage is within the normal operating voltage range.

CONDITIONS FOR SETTING THE DTC
The DTC will set if one of the following conditions occur:
^ A valid ID message is not received by the SDM within 5 seconds of the EFS Left being powered up
^ A status message is not received
^ The SDM has failed twice to reset the EFS Left

ACTION TAKEN WHEN THE DTC SETS
The SDM commands the AIR BAG indicator ON 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
Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and the connectors may result in misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:
^ A short between the EFS Left circuits
^ A short to ground, short to voltage, open, or high resistance in the EFS Left circuits.
^ The EFS Left connector
^ An internal EFS Left malfunction
^ The SDM connector
^ An internal SDM malfunction

If an intermittent condition exists, refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-12:

The numbers below refer to the step numbers on the diagnostic table:
2. Tests to see if the EFS Left connector is damaged or corroded.
3. Tests to see if the EFS Left terminals are damaged or corroded.
4. Tests to see if the SDM connector is damaged or corroded.
5. Tests to see if the SDM terminals are damaged or corroded.
6. Tests to see if there is a short between the two EFS Left circuits.
7. Tests to see if there is an open or a high resistance in the two EFS Left circuits.
8. Tests to see if there is a short to ground or a short to voltage in the two EFS Left circuits.