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 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 Intermittents and Poor Connections Diagnosis and Testing for Electrical Intermittents .
Use a J35616-A when probing or checking electrical connector terminals. The J35616-A 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 which 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 |
Ensure that the engine is left in the OFF position. 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 4 | Go to Step 3 | |
3 | Refer to the Scan Tool manufactures instruction manual for troubleshooting instructions. Has the troubleshooting/repair been properly completed? | -- | Go to Step 1 | -- |
4 | 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 3 |
Did you find and correct the condition? | -- | Go to the applicable Diagnostic System Check | Go to Step 6 | |
Test the DLC ground circuits at terminals 4 and 5 for an open. Refer to Testing for Continuity . Did you find and correct an improper condition? | -- | Go to the applicable Diagnostic System Check | Go to Step 7 | |
7 | Check for B+ voltage on pin 16. Is B+ voltage present? | -- | Go to Step 8 | Go to Step 11 |
8 | Test the class 2 serial data circuit for an open or short to ground in CKT 1807. Refer to Troubleshooting with a Digital Multimeter . Did you find and correct an improper condition? | -- | Go to the applicable Diagnostic System Check | Go to Step 9 |
Disconnect each module one at a time while monitoring the class 2 circuit for a short. Is the short removed after a module is disconnected? | -- | Go to Step 10 | Go to Step 9 | |
10 | Replace/repair the last module that was disconnected. Is the repair complete? | -- | Go to the applicable Diagnostic Circuit Check | Go to Intermittents and Poor Connections Diagnosis or Testing for Electrical Intermittents |
11 | Repair the open or high resistance in CKT 840. Refer to Wiring Repairs or Repairing Connector Terminals . Is the repair complete? | -- | Go to the applicable Diagnostic Circuit Check | Go to Step 1 |
