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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Optra 🢒 DTC 🢒 DTC U2105

DTC U2105 Non European Emissions

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2105 Lost Communications With Engine Control Module (ECM)

Conditions for Setting the DTC

The transmission control module (TCM) detects that the BUS OFF signal. This detection is continued for 0.2 seconds.

Action Taken When the DTC Sets
    • TCM will request the illumination of the hold lamp and store the DTC when the TCM detects a failure on the 1st ignition cycle
    • TCM judges the throttle opening is 0 percent for shift point and lock-up point control
    • TCM judges the throttle opening is 100 percent for line pressure control
    • No lock-up
    • No self-learning control
    • TCM judges the engine revolution is 0 RPM

Conditions for Clearing the DTC
    • The TCM turns off the hold lamp when no further failures are detected on the next ignition cycles.
    • The scan tool can clear the DTC from the TCM history.
    • The TCM detects the BUS normal signal for 2 seconds continuously.

Cause for Failure
    • Wiring harness or connector between engine control module (ECM) and TCM
    • ECM
    • TCM

Step

Action

Values

Yes

No

1
  1. Turn OFF the ignition.
  2. Install the scan tool.
  3. Turn ON the ignition, with the engine OFF.
  4. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu.
  5. Store Freeze Frame/Failure Records.
  6. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu.
  7. Clear DTC Information.
  8. Perform one vehicle drive cycle.

Is the hold lamp ON?

--

Go to Step 2

Go to Step 6

2
  1. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu.
  2. Request DTC by Status.

Is DTC U2105 displayed?

--

Go to Step 3

Go to Step 6

3
  1. Turn OFF the ignition.
  2. Disconnect the transmission control module (TCM) wiring connector and engine control module (ECM) wiring connector.
  3. Measure the resistance between terminal A17 of the TCM wiring connector and terminal 88 of the ECM wiring connector.
  4. Measure the resistance between terminal A7 of the TCM wiring connector and terminal 57 of the ECM wiring connector.

Is the resistance equal to the specified value?

0 ohms

Go to Step 4

Go to Step 5

4
  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage of terminal A17.
  3. Measure the voltage of terminal A7.

Is the voltage within the specified range?

11-14 V

Go to Step 5

Go to Step 7

5

Repair the malfunctioning terminals as necessary.

Did you complete the repair?

--

System OK

--

6

Repair the temporary connection failure of the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .

Did you complete the repair?

--

System OK

--

7
  1. Replace the TCM. Refer to Transmission Control Module Replacement .
  2. Turn OFF the ignition.
  3. Turn ON the ignition, with the engine OFF.
  4. Check if DTC U2105 is set.

Is the DTC set?

--

Go to Step 8

Go to Step 9

8

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 9

--

9
  1. After the repair, use a scan tool clear info function and road test the vehicle.
  2. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 1

System OK

DTC U2105 European Emissions

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2105 Lost Communications With Engine Control Module (ECM)

Conditions for Setting the DTC

The transmission control module (TCM) detects that the BUS OFF signal. This detection is continued for 0.2 seconds.

Action Taken When the DTC Sets
    • TCM will request the illumination of the malfunction indicator lamp (MIL) and store the DTC when the TCM detects a failure on the 1st ignition cycle
    • TCM judges the throttle opening is 0 percent for shift point and lock-up point control
    • TCM judges the throttle opening is 100 percent for line pressure control
    • No lock-up
    • No self-learning control
    • TCM judges the engine revolution is 0 RPM

Conditions for Clearing the DTC
    • The TCM turns off the MIL when no further failures are detected on the next ignition cycles.
    • The scan tool can clear the DTC from the TCM history.
    • The TCM detects the BUS normal signal for 2 seconds continuously.

Cause for Failure
    • Wiring harness or connector between engine control module (ECM) and TCM
    • ECM
    • TCM

Step

Action

Values

Yes

No

1
  1. Turn OFF the ignition.
  2. Install the scan tool.
  3. Turn ON the ignition, with the engine OFF.
  4. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu.
  5. Store Freeze Frame/Failure Records.
  6. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu.
  7. Clear DTC Information.
  8. Perform one vehicle drive cycle.

Is the malfunction indicator lamp (MIL) ON?

--

Go to Step 2

Go to Step 6

2
  1. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu.
  2. Request DTC by Status.

Is DTC U2105 displayed?

--

Go to Step 3

Go to Step 6

3
  1. Turn OFF the ignition.
  2. Disconnect the transmission control module (TCM) wiring connector and engine control module (ECM) wiring connector.
  3. Measure the resistance between terminal A17 of the TCM wiring connector and terminal 88 of the ECM wiring connector.
  4. Measure the resistance between terminal A7 of the TCM wiring connector and terminal 57 of the ECM wiring connector.

Is the resistance equal to the specified value?

0 ohms

Go to Step 4

Go to Step 5

4
  1. Turn ON the ignition.
  2. Measure the voltage of terminal A17.
  3. Measure the voltage of terminal A7.

Is the voltage within the specified range?

11-14 V

Go to Step 5

Go to Step 7

5

Repair the malfunctioning terminals as necessary.

Did you complete the repair?

--

System OK

--

6

Repair the temporary connection failure of the connector. Refer to Wiring Harness and Connector Inspection Diagnosis .

Did you complete the repair?

--

System OK

--

7
  1. Replace the TCM. Refer to Transmission Control Module Replacement .
  2. Turn OFF the ignition.
  3. Turn ON the ignition, with the engine OFF.
  4. Check if DTC U2105 is set.

Is the DTC set?

--

Go to Step 8

Go to Step 9

8

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 9

--

9
  1. After the repair, use a scan tool clear info function and road test the vehicle.
  2. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 1

System OK