GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2003 🢒 CTS - RHD 🢒 Body and Accessories 🢒 Data Link Communications 🢒 DTC U2100

Circuit Description

The controller area network (CAN) serial data line is a high speed serial data bus used to communicate information between the engine control module (ECM) and the transmission control module (TCM). Typical data-transmission speeds must be high enough to ensure that the required real-time response is maintained.

The CAN serial data line does not communicate with the scan tool via the DLC. CAN serial data information is interpreted by the ECM and transmitted to the serial data line by the ECM.

Conditions for Running the DTC

The CAN circuits are monitored continuously by the modules on the circuit. The only requirement is that the modules are in a RUN power mode.

Conditions for Setting the DTC

The module setting the DTC has attempted to establish communications on the CAN circuits for more than 5 seconds.

Action Taken When the DTC Sets

The module uses a default value for the missing parameter.

Conditions for Clearing the MIL/DTC
    • A current DTC clears and the MIL is turned OFF when the fault is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the fault.

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views

1

Did you perform the Diagnostic System Check for the system exhibiting the symptom?

Go to Step 2

Go to Control Module References in Body Control System

2
  1. Connect a scan tool to the vehicle.
  2. Use the scan tool in order to clear the DTC.
  3. Turn OFF the ignition.
  4. Disconnect the TCM.
  5. Turn the ignition ON, with the engine OFF.
  6. Use the scan tool to view DTCs in the ECM.

Does the DTC U2100 reset?

Go to Step 3

Go to Step 4

3
  1. Turn OFF the ignition.
  2. Disconnect the ECM and TCM connectors.
  3. Test both the CAN high and low circuits for the following conditions:
    4. • A short to ground
    • A short to voltage
    • A short to each other

Turn ON the ignition, with the engine OFF when you test 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 8

Go to Step 5

4

Inspect for poor connections at the TCM harness connector. 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 8

Go to Step 6

5

Inspect for poor connections at the ECM harness connector. 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 8

Go to Step 7

6

Important: Perform the programming or set-up procedure for the replaced control module, if required.

Replace the TCM. Refer to Control Module References in Body Control System.

Did you complete the replacement?

Go to Step 8

--

7

Important: Perform the programming or set up procedure for the replaced control module if required.

Replace the ECM. Refer to Control Module References in Body Control System.

Did you complete the replacement?

Go to Step 8

--

8
  1. Reconnect all modules not already connected.
  2. Use the scan tool in order to clear the DTCs.
  3. Turn OFF the ignition switch.
  4. Wait at least 10 seconds.
  5. Turn the ignition ON, with the engine OFF.
  6. Retrieve DTCs from the ECM and TCM.

Does the DTC reset ?

Go to Step 2

System OK