Chart D - SDM Cannot Communicate With Scan Tool

CIRCUIT DESCRIPTION
With the Sensing and Diagnostic Module (SDM) powered up and a scan tool connected to the data link connector (DLC) communications should be possible. Circuit 1807 connects the SDM to pin 1 of the DLC and the scan tool. The ground circuit 350 (to DLC pin 4) is also needed to complete the communication circuit with the SDM.

CHART TEST DESCRIPTION
The numbers below refer to the step numbers listed on the diagnostic chart.
Step 1. This step checks the scan tool's ability to power up.
Step 2. This step uses the scan tool's error screens to assist with diagnosis.
Step 3. This step checks for sufficient battery voltage to power up a scan tool.
Step 4. This step checks for an open body fuse.
Step 5. This step checks for a short to ground in circuit 350 and the scan tool.
Step 9. This step prompts you to check all possible causes of a faulty communications circuit.
Step 10. This step is to determine whether the SDM or scan tool is at fault.
Step 15. Is a reminder to perform the Diagnostic System Check after completing all SIR system repairs. Diagnostic System Check

DIAGNOSTIC AIDS
Some scan tools use pin 16 of the DLC and pin 4 to power up the tool, while others have their own batteries or use the cigar lighter. All scan tools must use pin 1 of the DLC to communicate with this vehicle.

Always perform the "SIR Diagnostic System Check" before using this chart.

When measurements are requested in this chart, use SA 91114NE digital multimeter with correct terminal adapter from SA 9206Z. When a check for proper connection is requested, refer to "Intermittent and Poor Connections." When a wire connector or terminal repair is requested, use the proper repair parts and refer to "Wiring Repair." Intermittents and Poor Connections

NOTICE: Perform "SIR DIAGNOSTIC SYSTEM CHECK" before proceeding with this chart.

NOTE: Air bag telltale will remain On after the same DTC appears twice and is stored in memory as a history code. If the air bag telltale is On, the DTC can be a current or history code.