B0077

CIRCUIT DESCRIPTION

SIR Schematics (Pickup): DLC, Inflatable Restraint Sensing And Diagnostic Module:

SIR Schematics (Utility): DLC, Fuse Block, Inflatable Restraint Sensing And Diagnostic Module:

SIR Schematics (Utility): Side Impact Sensors, Diagnostic Module:

SIR Schematics (30 Series Pickup): Fuse Block, Inflatable Restraint Sensing And Diagnostic Module:

IMPORTANT: This DTC is also used for the inflatable restraint electronic frontal sensor (EFS) found on the 35/36 series trucks. The 35/36 series trucks have one EFS located at the front of the vehicle. The EFS is diagnosed the same way as the inflatable restraint side impact sensor (SIS) used on Utility models. The following diagnostics will refer to the left SIS or the EFS depending on what series truck you are diagnosing.

The SIS/EFS circuit consists of a SIS/EFS, the SIS/EFS signal circuit, and the SIS/EFS voltage circuit. When the ignition is turned ON, the inflatable restraint sensing and diagnostic module (SDM) performs tests to diagnose critical malfunctions within itself. The SDM provides input power to the SIS/EFS. When input power is first detected, the SIS/EFS responds by performing internal diagnostics. The SIS/EFS then 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 SIS/EFS is powered up. The SIS/EFS will continually communicate a status message to the SDM. The SDM is capable of resetting the SIS/EFS 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
^ A valid ID message is not received within 5 seconds of the left SIS/EFS being powered up.
^ Status message is not received.
^ The SDM has failed twice to reset the left SIS/EFS.

ACTION TAKEN WHEN THE DTC SETS
^ The SDM commands ON the AIR BAG indicator via Class 2 serial data.
^ The SDM attempts to reset the left SIS/EFS.

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 left SIS/EFS signal and voltage circuits
^ High or low resistance in the left SIS/EFS signal and voltage circuits
^ Inspect the left SIS/EFS signal and voltage circuits carefully for cutting and/or chafing

Refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION

Steps 1-11:

The numbers below refer to the step numbers on the diagnostic table:
4. Tests for a short to ground, a high resistance, or an open in the left SIS/EFS signal circuit.
5. Tests for a short to ground, a high resistance, or an open in the left SIS/EFS voltage circuit.
6. Tests for a short to voltage in the left SIS/EFS signal circuit.
7. Tests for a short to voltage in the left SIS/EFS voltage circuit.