Circuit Description
The UART Serial Data Line is used for communication with the SIR Module. The UART line relies on a 5 volt digital signal for the exchange of data between different control modules and to provide Scan Tool diagnostic data. When the ignition switch is in the RUN position and the UART line is at rest, i.e., no communication is taking place, the voltage remains HIGH at approximately 5 volts. When data is transmitted the voltage is pulled to ground, approximately 0 volts. The Supplemental Inflatable Restraint System's Sensing and Diagnostic Module (SDM) utilizes UART communications. The Scan Tool may be used to retrieve, view, and clear Diagnostic Trouble Codes (DTCs) stored in the SDM. The Scan Tool also uses the UART line to receive serial data from the SDM. A loss of UART communications would prevent the Scan Tool from communicating with the SDM during SIR system diagnosis.
Diagnostic Aids
IMPORTANT: Refer to SIR Service Precautions before doing SIR system repairs or service.
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If the Scan Tool will not function, refer to Scan Tool Does Not Power Up
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If the condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections and Testing for Electrical Intermittents in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Can the scan tool be powered up? | -- | |||
Does the Scan Tool communicate on the UART data line? | -- | |||
3 | Refer to the Scan Tool manufacturer's instruction manual for troubleshooting instructions. Has the troubleshooting repair been properly completed? | -- | -- | |
4 | Inspect for proper connection and terminal tension of the scan tool to the Data Link Connector (DLC) terminal 9. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct a poor condition? | -- | ||
5 |
Did you find and correct a poor condition? | -- | ||
6 | Test for an open in CKT 800 (TAN) between the DLC and the SDM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
7 | Test for a short to ground in CKT 800 (TAN) between the DLC and the SDM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
8 | Test for a short to B+ in CKT 800 (TAN) between the DLC and the SDM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
9 |
Is the repair complete? | -- | -- |
