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Test Description

WARNING: This page is about a different car, the 2004 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  A communications failure to one or more modules of a data link circuit may cause the malfunction.
  2. 3:  If a module is not transmitting the required data, the module receiving the data cannot detect the presence of the transmitting module.
  3. 6:  The TCM needs time to reset memory.
DTC U2104

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 Did you perform either the Engine Controls, or Transmission, Diagnostic System Check? Go to Step 2  Go to Control Module References in Body Control System
2 
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, monitor the DTC Information for DTC U2100.
  4. With a scan tool, monitor the DTC Information for DTCs in the range of U2105 - U2106.
Does the scan tool indicate that DTC U2100 or DTCs in the range of U2105 - U2106 as either current or history DTCs?		 Go to Diagnostic Trouble Code (DTC) List  Go to Step 3 
3  Use the scan tool to observe the Data Lists of the ECM, TCM for the data listed:
  • Transmission Data (TCM):
    • Engine Speed (RPM) - This comes from the ECM.
    • MIL Request - This goes to the ECM.
  • Engine Data (ECM):
    • Transmission Speed - This comes from the TCM.
    • MIL Request - This comes from the TCM.

Either data missing or a mismatch between the data sent and received indicates a malfunction
Does either the lack of information in the data listed or a mismatch between the modules in the data listed indicate an inoperative module?		 Go to Step 4  Go to Step 6 
4 Inspect for poor connections at the harness connector of the module that is not communicating. 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 9  Go to Step 5 
5
IMPORTANT: Perform the programming or set up procedure for the replaced control module if required.
Replace the control module that is not communicating. Refer to Control Module References in Body Control System.Did you complete the replacement?		 Go to Step 6  -
6 
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition switch.
  3. Wait at least 10 seconds.
  4. Turn the ignition ON, with the engine OFF.
  5. Retrieve DTCs from the ECM and TCM.
Does the DTC reset ?		 Go to Step 7  System OK
7 Inspect the connector of the module recording the DTC. 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 9  Go to Step 8 
8
IMPORTANT: Perform the programming or set up procedure for the replaced control module if required.
Replace the control module that has set the DTC. Refer to Control Module References in Body Control System.Did you complete the replacement?		 Go to Step 9  -
9
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition switch.
  3. Wait at least 10 seconds.
  4. Turn the ignition ON, with the engine OFF.
  5. Retrieve DTCs from the ECM and TCM.
Does the DTC reset ?		 Go to Step 2  System OK
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