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For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2007 🢒 VUE - FWD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 DTC U2104

Circuit Description

Modules connected to the controller area network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. If no communication is detected on CAN serial data circuit, the DTC is set. A total non communication condition may be caused by a short to battery or voltage on any of the CAN circuits or a short between the CAN high and low circuits.

The following modules communicate on CAN serial data bus:

    • The body control module (BCM)
    • The electronic brake control module (EBCM), if equipped
    • The engine/powertrain control module (ECM/PCM)
    • The transmission control module (TCM), with L61

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2104 Controller Area Network (CAN) Bus Reset Counter Overrun

Conditions for Running the DTC
    • Voltage supplied to the modules is in the normal operating voltage range.
    • The vehicle power mode requires communication to occur.

Conditions for Setting the DTC

A total non communication condition is detected on CAN serial data circuit.

Conditions for Clearing the MIL/DTC
    • A current DTC and malfunction indicator lamp (MIL) clear when the malfunction is no longer present.
    • A history DTC clears when requested by the scan tool or when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Step

Action

Yes

No

Schematic Reference: Data Communication Schematics

Connector End View Reference: Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition.
  2. Disconnect all modules that communicate on controller area network (CAN) bus.
  3. Test all CAN serial data circuits between modules for the following:
    4. • Short to ground
    • Short to voltage
    • Open
    • Short between CAN high and CAN low circuits
  4. Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Refer to the following:

Did you find and correct the condition?

Go to Step 8

Go to Step 3

3
  1. Reconnect the body control module (BCM).
  2. Turn ON the ignition, with the engine OFF.
  3. Retrieve DTCs from the BCM.

Does the DTC U2104 still set as current?

Go to Step 6

Go to Step 4

4

Repeat the following steps until the DTC is set or all modules are connected.

  1. Turn OFF the ignition.
  2. Reconnect the other disconnected modules one at a time in the following order:
    3. 2.1. Electronic brake control module (EBCM), if equipped
    2.2. Transmission control module (TCM), w/L61
    2.3. Engine control module (ECM)/powertrain control module (PCM)
  3. Turn ON the ignition, with the engine OFF.
  4. Retrieve DTCs from the first connected module, in the previous step.

Does the scan tool displays DTC U2104 as current?

Go to Step 5

Go to Testing for Intermittent Conditions and Poor Connections

5
  1. Turn OFF the ignition.
  2. Disconnect the last module connected.
  3. Inspect for poor connections at CAN serial data circuits of the suspected module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6
  1. Turn OFF the ignition.
  2. Disconnect the BCM.
  3. Inspect for poor connections at CAN serial data circuits of the suspected module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 8

Go to Step 7

7

Replace the suspected module. Refer to Control Module References for replacement, setup and programming.

Did you complete the replacement?

Go to Step 8

--

8
  1. Connect all modules and connectors.
  2. Connect the scan tool to the DLC.
  3. Turn ON the ignition, with the engine OFF.
  4. Retrieve DTCs.

Is the DTC U2104 still set as current?

Go to Step 2

System OK