Rodeo S 2WD L4-2.2L (1999)
Sensing And Diagnostic Module: Description and Operation
WARNING: DURING SERVICE PROCEDURES, BE VERY CAREFUL WHEN HANDLING A SENSING AND DIAGNOSTIC MODULE
(SDM). NEVER STRIKE OR JAR THE SDM. NEVER POWER UP THE SRS WHEN THE SDM IS NOT RIGIDLY ATTACHED TO THE
VEHICLE. ALL SDM AND MOUNTING BRACKET FASTENERS MUST BE CAREFULLY TORQUED AND THE ARROW MUST BE
POINTED TOWARD THE FRONT OF THE VEHICLE TO ENSURE PROPER OPERATION OF THE SRS. THE SDM COULD BE
ACTIVATED WHEN POWERED WHILE NOT RIGIDLY ATTACHED TO THE VEHICLE WHICH COULD CAUSE DEPLOYMENT
AND RESULT IN PERSONAL INJURY.
The Sensing and Diagnostic Module (SDM) is designed to perform the following functions in the SRS:
1. Energy Reserve - The SDM maintains 24-Volt Loop Reserve (24VLR)energy supply to provide deployment energy when ignition voltage is lost
in a frontal crash.
2. Frontal Crash Detection - The SDM monitors vehicle velocity changes to detect frontal crashes which are severe enough to warrant deployment.
3. Air Bag Deployment - When a frontal crash of sufficient force is detected, the SDM will cause enough current to flow through the air bag
assembly to deploy the air bag.
4. Malfunction Detection - The SDM performs diagnostic monitoring of SRS electrical components and sets a diagnostic trouble code when a
malfunction is detected.
5. Frontal Crash Recording - The SDM records information regarding SRS status during frontal crash.
6. Malfunction Diagnosis - The SDM displays SRS diagnostic trouble codes and system status information through the use of a scan tool.
7. Driver Notification - The SDM warns the vehicle driver of SRS malfunctions by controlling the "Air Bag" warning lamp.
The SDM is connected to the SRS wiring harness by a 24-pin connector. This harness connector uses a shorting clip across certain terminals in the
contact area. This shorting clip connects the "AIR BAG" warning lamp to ground when the SDM harness connector is disconnected or CPA (Connector
Position Assurance) is not inserted even if completely connected. This will cause the "AIR BAG" warning lamp to come "ON" steady whenever the
ignition switch is at the ON or START positions with the SDM disconnected.
