Data Link Communications Schematic Icons
Data Link Communications Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 1: A DTC U1001 - U1254 Lost Communications with XXX with a history status may indicate the cause of U1000 or U1255.
- 2: The modules not communicating are the likely cause of DTC U1000 or U1255. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
- 6: The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 Lost Communications with XXX for those modules that it was monitoring.
- 9: The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
- 12: If all modules are communicating, the module which set DTC U1000 or U1255 may have done so due to some other condition.
- 14: The module which set U1000 or U1255 is the likely cause of the malfunction.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems | |||
| 1 | Install a scan tool. Turn ON the ignition, with the engine OFF. Record the DTCs set in by each module. If using a Tech 2, use the Class 2 DTC Check feature to determine which modules have DTCs set. Did you record any DTCs in the range of U1001-U1254 with a history status? | Go to DTC U1001-U1254 | Go to Step 2 |
| 2 | Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the class 2 Message Monitor feature. Record all of the modules communicating on the class 2 serial data circuit. Compare the list of modules which are communicating to the list given in the Description and Operation. Refer to Data Link Communications Description and Operation . Does every module on the class 2 serial data circuit communicate? | Go to Step 12 | Go to Step 3 |
| 3 | Test the following circuits of the module that is not communicating for an open or short to ground: The battery positive voltage supply circuits The switched battery positive supply circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits Refer to the following: Control Module References in Body Control System for the applicable schematic Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 8 | Go to Step 4 |
| 4 | Turn OFF the ignition. Test the ground circuits of the module that is not communicating for an open. Refer to the following: Control Module References in Body Control System for the applicable schematic Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 8 | Go to Step 5 |
| 5 | IMPORTANT: Inspect all connectors in the serial data communications circuit. Refer to the following: Data Link Connector (DLC) Schematics Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Turn OFF the ignition. Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to the following: Data Link Connector (DLC) Schematics Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 8 | Go to Step 6 |
| 6 | Inspect the harness connector of the module that is not communicating for poor connections and terminal tension at the following circuits: The battery positive voltage input circuits The switched battery positive voltage supply The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The ground circuits The class 2 serial data circuits Refer to the following: Control Module References in Body Control System for the applicable schematic Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 8 | Go to Step 7 |
| 7 | IMPORTANT: Perform the module programming or setup procedure if required. Replace the module that is not communicating. Refer to Control Module References in Body Control System for the appropriate Repair Instructions for the module replacement.Did you complete the replacement? | Go to Step 10 | |
| 8 | Turn ON the ignition, with the engine OFF. Select the Display DTCs function for the module which was not communicating. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Control Module References in Body Control System for applicable Diagnostic System Check | Go to Step 9 |
| 9 | Clear the DTCs with the scan tool. Did you complete the action? | Go to Step 10 | |
| 10 | Select the Display DTCs function for the modules which had U1000 or U1255 set as a current DTC. Does the scan tool display DTCs which do not begin with a "U"? | Go to Control Module References in Body Control System for applicable Diagnostic System Check | Go to Step 11 |
| 11 | Clear the DTCs with the scan tool. Did you complete the action? | System OK | |
| 12 | Did you record any other DTCs for the modules which had U1000 or U1255 set as a current DTC? | Go to Control Module References in Body Control System for applicable Diagnostic System Check | Go to Step 13 |
| 13 | Turn ON the ignition, with the engine OFF. Clear the DTCs with the scan tool. Turn OFF the ignition for at least 5 seconds. Turn ON the ignition, with the engine OFF. Select the Display DTCs function with the scan tool. Does the scan tool display U1000 or U1255 set as a current DTC? | Go to Step 14 | Go to Diagnostic Aids |
| 14 | IMPORTANT: Perform the module programming or setup procedure if required. Replace the module which had U1000 or U1255 set as a current DTC. Refer to Control Module References in Body Control System for the appropriate Repair Instructions for the module replacement.Did you complete the replacement? | System OK | |
| IMPORTANT |
|---|
| Inspect all connectors in the serial data communications circuit. Refer to the following: Data Link Connector (DLC) Schematics Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems |
| IMPORTANT |
|---|
| Perform the module programming or setup procedure if required. |
| IMPORTANT |
|---|
| Perform the module programming or setup procedure if required. |
DTC U1000 & U1255
The number below refers to the step number on the diagnostic table.
- 6: The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems | |||
| 1 | Test the following circuits of the module that is not communicating for an open or a short to ground: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage circuits Refer to the following: Control Module References in Body Control System for the applicable schematic Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 6 | Go to Step 2 |
| 2 | Turn OFF the ignition. Test the ground circuits of the module that is not communicating for an open. Refer to the following: Control Module References in Body Control System for the applicable Schematic Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 6 | Go to Step 3 |
| 3 | Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
| 4 | Inspect the harness connectors of the module that is not communicating for poor connections and terminal tension at the following circuits: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage supply circuits The ground circuits The class 2 serial data circuits Refer to the following: Control Module References in Body Control System for the applicable schematic Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
| 5 | IMPORTANT: Perform the programming or set up procedure for the module, if required. Replace the module that is not communicating. Refer to Control Module References for the applicable replacement procedure.Did you complete the replacement? | Go to Step 6 | |
| 6 | Install a scan tool. Turn ON the ignition, with the engine OFF. Select the Display DTCs function for the module which was not communicating. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Control Module References for the applicable Diagnostic System Check | Go to Step 7 |
| 7 | Select the Display DTCs function for the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"? | Go to Control Module References for the applicable Diagnostic System Check | Go to Step 8 |
| 8 | Clear the DTCs with the scan tool. Continue diagnosing or clearing the DTCs until all of the modules have been diagnosed and all of the DTCs have been cleared. Did you complete the action? | Go to Control Module References for the applicable Diagnostic System Check | |
| IMPORTANT |
|---|
| Perform the programming or set up procedure for the module, if required. |
DTC U1001-U1254
The number below refers to the step number on the diagnostic table.
- 4: If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Data Link Communications Connector End Views | |||
| 1 | Test the battery positive voltage circuit of the Data Link Connector (DLC) for an open or a short to ground. Refer to Circuit Testing or 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 2 |
| 2 | Test the ground circuit from pin 4 of the DLC for an open or high resistance. Refer to Circuit Testing or 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 3 |
| 3 | Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections or Connector 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 4 |
| 4 | The scan tool may be malfunctioning. Refer to the scan tool user guide. Did you obtain a properly operating scan tool? | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | |
Scan Tool Does Not Power Up
The numbers below refer to the step numbers on the diagnostic table.
- 2: A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
- 4: The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition. U1300 U1301 U1305
- 6: A State of Health DTC with a history status may be present along with a U1000 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
- 10: Normal class 2 serial data communication cannot take place until the Body Control Module (BCM) sends the appropriate power mode message. If the BCM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate. Early 2004 model vehicles have a redundant class 2 serial data circuit between the BCM and PCM. Late 2004 model vehicles do not have this circuit and it is not necessary to disconnect the PCM to perform this step.
- 12: Normal class 2 serial data communication cannot take place until the Body Control Module (BCM) sends the appropriate power mode message. If the BCM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
- 17: If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.
- 18: The communication concern may have prevented diagnosis of the customer complaint.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems | |||
| 1 | Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up |
| 2 | Turn ON the ignition, with the engine OFF. Attempt to communicate with each module on the class 2 serial data circuit. Does the scan tool communicate with any module on the class 2 serial data circuit? | Go to Step 3 | Go to Step 8 |
| 3 | Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all of the displayed DTCs, the DTC status and the module which set the DTC. Did you record any DTCs in the range of U1000 to U1305? | Go to Step 4 | Go to Step 7 |
| 4 | Are history 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: Testing for Intermittent Conditions and Poor Connections Circuit Testing Connector Repairs Wiring Repairs Did you find and correct the condition? | Go to Step 16 | Go to Step 6 |
| 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 |
| 7 | Diagnose the non communicating module by using the DTC U1001-U1254 Lost Communications with XXX procedure for the module which is not communicating. The DTC U1001-U1254 Lost Communications with XXX procedure will determine which module is not communicating. Refer to DTC U1001-U1254 . Did you complete the action? | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | |
| 8 | Turn OFF the ignition. Disconnect the scan tool from the data link connector (DLC). Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector 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 |
| 9 | Test the signal ground circuits of the DLC for an open or high resistance. Refer to Testing for Intermittent Conditions and Poor Connections and Connector 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 |
| 10 | Remove the class 2 serial data splice pack comb. Disconnect the Powertrain Control Module (PCM) if the vehicle is an early 2004 model. Using the correct terminal adapter and jumper wire at the spice pack, connect a jumper between the DLC and the Body Control Module (BCM). Attempt to communicate with the BCM. Does the scan tool communicate with the BCM? | Go to Step 12 | Go to Step 11 |
| 11 | Test the class 2 serial data circuit(s) to the BCM for the following conditions. Turn ON the ignition when testing for a short to voltage: High resistance Open Short to ground Short to voltage Test the following circuits of the BCM for an open or high resistance: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage supply circuits The ground circuits Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition? | Go to Step 16 | Go to Step 14 |
| 12 | IMPORTANT: The BCM must remain connected to the DLC. Use the appropriate jumper if needed. Using the correct terminal adapter and jumper wire at the splice pack, perform the following in order to determine which class 2 serial data circuit or module is causing the concern: Turn ON the ignition, with the engine OFF. Using the correct terminal adapter and jumper wire, connect each previously disconnected module to the class 2 serial data circuit one at a time until communication with the class 2 serial data circuit is lost. Did you complete the action? | Go to Step 13 | |
| 13 | Test the class 2 serial data circuits to the suspect module 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 16 | Go to Step 14 |
| 14 | Inspect for poor connections and terminal tension at the harness connector of the suspect module. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 15 |
| 15 | IMPORTANT: Perform the module programming or setup procedure if required. Replace the suspect module. 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 16 | |
| 16 | Connect all of the modules. Connect all the connectors. Install a scan tool. Turn ON the ignition leaving the engine OFF. 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. Wait for 10 seconds. Select the display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set. Record all of the displayed DTCs and the DTC status. Did your record any DTCs which begin with a letter "U" and with a current status? | Go to Step 18 | Go to Step 17 |
| 17 | Did you record any DTCs which do not begin with a letter "U"? | Go to Step 18 | Go to Step 19 |
| 18 | Diagnose the DTCs as directed by the diagnostic procedures for the particular module or concern. Did you complete the action? | Go to Step 19 | |
| 19 | Did you diagnose all of the DTCs? | Go to Step 20 | Go to Step 18 |
| 20 | Clear the DTCs using the scan tool. Did you complete the action? | Go to Control Module References in Body Control System for the applicable Diagnostic System Check | |
| 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. |
| IMPORTANT |
|---|
| The BCM must remain connected to the DLC. Use the appropriate jumper if needed. |
| IMPORTANT |
|---|
| Perform the module programming or setup procedure if required. |
| 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. |
Scan Tool Does Not Communicate With Class 2 Device
See also:
• Master Electrical Component List