Circuit Description
Modules connected to the Class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a Scan Tool to the Data Link Connector (DLC) allows communication with the modules for diagnostic purposes.
The diagnostic procedure assumes that all modules are powered. When you are uncertain whether this condition is met, perform the Diagnostic System Check for the module in question. Diagnostic trouble codes (DTCs) may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure that all the DTCs are diagnosed and cleared from memory.
Diagnostic Aids
If the malfunction is intermittent, refer to Testing for Intermittent Conditions and Poor Connections and Testing for Electrical Intermittents in Wiring Systems.
Use a J 35616 when probing or checking electrical connector terminals. The J 35616 prevents terminal damage and inspects for proper terminal contact tension.
Disconnecting modules and turning the ignition switch to the RUN position may cause DTCs in these modules. Inspect for DTCs in each module upon completion of the required repair.
Ensure that the theft deterrent system has not caused a Class 2 No Communication malfunction.
Test Description
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This step isolates the fault to the vehicle or the Scan Tool.
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This step inspects the integrity of the ground to the Scan Tool.
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This step inspects the integrity of the power to the Scan Tool.
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This step inspects for a faulty module causing the Class 2 line to be shorted to ground.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Does the Scan Tool power up? | -- | Go to Step 2 | Go to Step 7 |
If using a Tech 2, obtain this information using the Class 2 message monitor feature. Does the Scan Tool communicate with any modules on the Class 2 serial data circuit? | -- | Go to Step 3 | Go to Step 4 | |
3 | Attempt to use any other forms of communication (i.e., UART communication, Remote Keyless Entry system programming). Does the Scan Tool perform all available functions? | -- | Go to Step 5 | Go to Step 4 |
4 | Refer to the Scan Tool manufacturer's instruction manual for troubleshooting instructions. Has the troubleshooting/repair been properly completed? | -- | Go to Control Module References for the applicable System Check | -- |
Did you find and correct the condition? | -- | Go to Control Module References for the applicable System Check | Go to Step 6 | |
Test the DLC ground CKT 150 (BLK) at terminal 4 and CKT 451 (BLK/WHT) CKT 551 (TAN/WHT) at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct an improper condition? | -- | Go to Control Module References for the applicable System Check | Go to Step 7 | |
7 | Check for B+ voltage at pin 16 for CKT 840 (ORN). Is B+ voltage present? | -- | Go to Step 8 | Go to Step 11 |
8 | Test the class 2 serial data CKT 1807 (PPL) for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct an improper condition? | -- | Go to Control Module References for the applicable System Check | Go to Step 9 |
Disconnect each module one at a time while monitoring the class 2 serial data CKT 1807 (PPL) for a short to ground. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Is the short removed after a module is disconnected? | -- | Go to Step 10 | Go to Step 12 | |
10 | Replace/repair the last module that was disconnected. Is the repair complete? | -- | Go to Control Module References for the applicable System Check | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
11 | Repair the open or high resistance in CKT 840 (ORN). Refer to Wiring Repairs or Repairing Connector Terminals in Wiring Systems. Is the repair complete? | -- | Go to Control Module References for the applicable System Check | -- |
12 | Repair the open or high resistance in CKT 1807 (PPL). Refer to Wiring Repairs or Repairing Connector Terminals in Wiring Systems. Is the repair complete? | -- | Go to Control Module References for the applicable System Check | -- |
