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 engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.
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 DTC U1300 and U1301 may be retrieved with a history status. These DTCs are not the cause of the present condition.
A State of Health DTC with a history status may be present along with a U1000 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on. Any additional DTCs beginning with "U" indicate a specific module is not communicating. The U1XXX test is used to diagnose this concern.
Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
An open in the class 2 serial data circuit between the DLC and connector C200 will prevent the scan tool from communicating with any module. This condition will not set a DTC.
The class 2 serial data circuit is shorted to voltage or to ground. This step isolates the concern to the five modules not linked through a fuse panel.
This step adds the rear fuse panel
This step adds the 3 modules linked through the rear fuse panel.
This step adds the modules linked in the engine compartment.
The modules in the 3 loops (base, interior and engine compartment) must be diagnosed in the following order:
Base -- body control module (BCM), instrument panel integration module (IPM), instrument panel cluster (IPC) and theft deterrent control module last.
Interior -- memory seat module (MSM), inflatable restraint sensing and diagnostic (SDM) module and remote control door lock receiver (RCDLR) last.
Engine Compartment -- powertrain control module (PCM) first and electronic brake control module (EBCM) second. The connector C101 is diagnosed last.
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 |
---|---|---|---|
1 | Does the scan tool power up? | Go to Step 2 | |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 3 | Go to Step 7 | |
Did you record any DTCs in the range of U1000 to U1305? | Go to Step 4 | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | |
4 | Are the DTCs U1300, U1301 or U1305 retrieved from any module? | Go to Step 5 | Go to Step 6 |
5 |
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 in Wiring Systems: Did you find and correct the condition? | Go to Step 28 | Go to Step 6 |
Are U1000 or U1255 the only DTCs displayed in the previously specified range? | Go to DTC U1000 and U1255 | Go to DTC U1001-U1254 | |
Did you find and correct the condition? | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | Go to Step 8 | |
8 | Test the ground circuit at terminal 5 of the DLC for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | Go to Step 9 |
Test the class 2 serial data circuit of the DLC for an open between terminal 2 and connector C200. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | Go to Step 10 | |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 11 | Go to Step 16 | |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 12 | Go to Step 26 | |
12 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 13 | Go to Step 27 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 14 | Go to Step 21 | |
14 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 15 | Go to Step 25 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 29 | Go to Step 21 | |
16 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 17 | Go to Step 21 |
17 |
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 18 | Go to Step 20 |
18 |
Did you find and correct the condition? | Go to Step 28 | Go to Step 19 |
19 |
Did you complete the replacement? | Go to Step 28 | -- |
20 |
Did you find and correct the condition? | Go to Step 28 | Go to Step 21 |
Perform the following, one module at a time starting at the module furthest from the DLC, for each module on the class 2 circuit now attached to the DLC.
Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 22 | Go to Step 25 | |
22 | Test the class 2 serial data circuit after the last module disconnected for a short to ground or a short to voltage. (Turn ON the ignition with the engine OFF when testing for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 28 | Go to Step 23 |
23 | Inspect for poor connections at the harness connector of the last module disconnected. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 28 | Go to Step 24 |
24 | Replace the last module disconnected. Refer to Control Module References in Body Control System for the appropriate Repair Instructions for module replacement. Did you complete the replacement? | Go to Step 28 | -- |
25 | Repair the class 2 serial data circuit(s) and in-line connector(s) between the last module disconnected in the branch being diagnosed. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 28 | -- |
26 |
Did you complete the replacement? | Go to Step 28 | -- |
27 |
Did you complete the replacement? | Go to Step 28 | -- |
Important: 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 or disconnect the scan tool before you display DTCs. Did you record any DTCs which begin with a "U" and with a current status? | Go to Step 30 | Go to Step 29 | |
Did you record any DTCs which do not begin with a "U"? | Go to Step 30 | Go to Step 32 | |
30 | Diagnose the DTCs as directed by the diagnostic procedures for the particular module or malfunction. The PCM may have DTC(s) P1602 to P1615, or P1626 set. If only P1600 DTC(s) in the range specified along with history U1xxx DTC(s) are set and the vehicle will start and run, the action is complete. Did you complete the action? | Go to Step 31 | -- |
31 | Did you diagnose all of the DTCs? | Go to Step 32 | Go to Step 30 |
32 | Use the scan tool in order to clear the DTCs. Did you complete the action? | System OK | -- |