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 engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The following conditions will cause a total loss of class 2 serial data communication:
• | A class 2 serial data circuit shorted to ground. |
• | A class 2 serial data circuit shorted to voltage. |
• | An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit. |
The numbers below refer to the step numbers on the diagnostic table.
A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. The following modules communicate on the class 2 serial data circuit:
• | The body control module (BCM) |
• | The electronic brake control module (EBCM) |
• | The inflatable restraint sensing and diagnostic module (SDM) |
• | The instrument panel cluster (IPC) |
• | The powertrain control module (PCM) |
• | The radio |
• | The rear seat entertainment (RSE) assembly |
• | The transfer case shift control module (TCSCM) |
• | The vehicle communication interface module (VCIM) |
The following DTCs may be retrieved with a history status, but are not the cause of the present condition.
• | U1300 |
• | U1301 |
• | U1305 |
A state of health DTC with a history status may be present along with a U1000 or U1255 code having a current status. This indicates that the malfunction occurred when the ignition was ON.
Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.
The communication malfunction may have prevented diagnosis of the customer complaint.
Step | Action | Yes | No | ||||||||||||||||
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Schematic Reference: Data Link Connector Schematics Connector End View Reference: Master Electrical Component List | |||||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||||||||
2 | Does the scan tool power up? | Go to Step 3 | |||||||||||||||||
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 4 | Go to Step 9 | |||||||||||||||||
Did you record any DTCs in the range of U1000 to U1305? | Go to Step 5 | Go to Step 8 | |||||||||||||||||
5 | Are the history DTCs U1300, U1301 or U1305 retrieved from any module? | Go to Step 6 | Go to Step 7 | ||||||||||||||||
6 |
Important:: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions. Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following: Did you find and correct the condition? | Go to Step 18 | Go to Step 7 | ||||||||||||||||
Are U1000 or U1255 the only DTCs displayed in the previously specified range? | Go to DTC U1000 and U1255 | Go to DTC U1001-U1254 | |||||||||||||||||
Diagnose the non-communicating module by using the DTC U1001-U1254 procedure for the module which is not communicating. Refer to DTC U1001-U1254 . Did you complete the action? | -- | ||||||||||||||||||
9 |
Did you find and correct the condition? | Go to Step 10 | |||||||||||||||||
10 | Test the DLC ground circuit at terminal 5 for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 11 | |||||||||||||||||
11 | Repeat the following steps on the class 2 serial data circuits until the communication with body control module (BCM) is established or all modules listed below were disconnected.
Does the scan tool communicate with the BCM? | Go to Step 12 | Go to Step 15 | ||||||||||||||||
12 |
Important: Perform this step only if the suspected module is IPC or Radio.
Did you find and correct the condition? | Go to Step 18 | Go to Step 13 | ||||||||||||||||
13 | Inspect for poor connections at the class 2 serial data circuit of the last disconnected module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 14 | ||||||||||||||||
14 | Replace the last disconnected module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 18 | -- | ||||||||||||||||
15 |
Did you find and correct the condition? | Go to Step 18 | Go to Step 16 | ||||||||||||||||
16 | Inspect for poor connections at the class 2 serial data circuit of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 18 | Go to Step 17 | ||||||||||||||||
17 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 18 | -- | ||||||||||||||||
The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF the scan tool prior to performing this test. Did you record any DTCs which begin with a "U" and with a current status? | Go to Step 19 | ||||||||||||||||||
Did you record any DTCs which do not begin with a "U"? | Go to Step 20 | ||||||||||||||||||
20 | Use the scan tool in order to clear the DTCs. Did you complete the action? | System OK | -- |