GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 VUE - FWD 🢒 Brakes 🢒 Hydraulic Brakes 🢒 DTC U2104

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), body control module (BCM), electronic brake control module (EBCM), 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 BCM and transmitted to the serial data line by the BCM.

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

Conditions for Running the DTC

The CAN circuits are monitored continuously by the modules on the circuit.

Conditions for Setting the DTC

The module setting the DTC has attempted to establish communications on the CAN circuits more than 7 times.

Action Taken When the DTC Sets

The DTC is set as both current and history, the modules on the CAN network each take separate actions as listed:

Engine control module (ECM) and body control module (BCM):

    • Turn ON the MIL during the second consecutive drive cycle with the error detected.
    • Record the operating conditions at the time of turning ON the MIL and store the data as Freeze Frame information.

Conditions for Clearing the MIL/DTC
    • A current DTC clears and the MIL is turned OFF when the fault is no longer detected after the 3rd consecutive drive cycle.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the fault, or does not reoccur after 40 consecutive drive cycles.
    • A history DTC clears is there is a battery disconnect.

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems.

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 for the applicable Diagnostic System Check

2
  1. Install the scan tool.
  2. With the scan tool, communicate with the BCM, ECM, and TCM.
  3. Monitor the DTC information for DTC U2100.

Does the scan tool indicate that DTC U2100 sets as either a current or history DTC?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

Inspect for poor connections at the harness connector of the module that is not communicating.

Did you find and correct the condition?

Go to Step 4

Go to Step 5

4

  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 the DTCs from the EBCM, ECM, BCM, and TCM.

Does the DTC reset?

Go to Step 2

System OK

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 for the applicable replacement procedure.

Did you complete the replacement?

Go to Step 4

--