For 1990-2009 cars

## DTC U2105 European and North American Emissions

### Circuit Description

Modules that are connected to the shared communication circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have pre-recorded information about what messages are needed to be exchanged on the serial data circuits for each virtual network. The messages are usually supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2105 CAN BUS Error

### Conditions for Running the DTC

The ignition is ON or the engine is running.

### Conditions for Setting the DTC

The transmission control module (TCM) detects that there is no signal on the CAN serial data high or serial data low circuit for more than 0.2 seconds.

### Action Taken When the DTC Sets

• | The TCM will store the DTC when a failure is detected on the first ignition cycle.

• | If communication between the TCM and the ECM resumes anytime after the storing of DTC P2105, a DTC P0700 will set in the ECM and illuminate of the malfunction indicator lamp (MIL).

• | The TCM can no longer determine the validity of any information it may or may not receive from the ECM. Therefore the TCM substitutes default values for engine speed, throttle position, and other engine data signals.

• | Transmission operation will be reduced, affecting shift points, torque converter clutch operation, and other driveability concerns.

### Conditions for Clearing the DTC

• | The TCM suspends the request for DTC P0700, when no further failures are detected on the next three ignition cycles.

• | The scan tool can clear the DTC from the TCM history.

### Diagnostic Aids

• | The TCM scan tool data parameters that are received from the ECM, will indicate zero when the CAN serial data circuit failure is active.

• | An intermittent malfunction may be caused by a fault in the electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections.

• | Repair any electrical circuit faults that were found. Refer to Wiring Repairs.

• | The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Automatic Transmission Controls Schematics Connector End View Reference: Component Connector End Views
1 | Did you perform the Diagnostic System Check - Transmission/Transaxle? | -- | Go to Step 2 | Go to Diagnostic System Check - Automatic Transmission
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Save the DTC and Freeze Frame information into the scan tool memory.
4. Perform the scan tool Clear DTC Information function for the transmission control module (TCM) and the engine control module (ECM).
5. Operate the vehicle for 1 minute or until the malfunction indicator lamp (MIL) illuminates.
6. Check the TCM for DTCs.

Is DTC U2105 displayed?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn OFF the ignition.
2. Disconnect connector A from the TCM.
3. Turn the ignition ON, with the engine OFF.
4. Measure the voltage between the CAN Serial Data High circuit at the connector and ground.
5. Measure the voltage between the CAN Serial Data Low circuit at the connector and ground.

Was the voltage within the specified values for both the high and the low CAN circuits?

1.5-3.4 V

Go to Step 6

Go to Step 4

4 |

1. Inspect the CAN serial data circuit with the incorrect voltage for the following:

• | Open circuit

• | Short to ground

• | Short to voltage

2. Repair as necessary. Refer to Wiring Repairs and Connector Repairs.

Did you find and correct a condition?

--

Go to Step 9

Go to Step 5

5 | Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct a condition? | -- | Go to Step 9 | Go to Step 8
6 | Inspect for poor connections at the harness connector of the TCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct a condition? | -- | Go to Step 9 | Go to Step 7
7 | Replace the TCM. Refer to Transmission Control Module Replacement. Did you complete the replacement | -- | Go to Step 9 | --
8 | Replace the ECM. Refer to Control Module References. 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 for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 10

Go to Step 2

10 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK

## DTC U2105 Non European and N. American Emission

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2105 BUS OFF Signal

### Conditions for Setting the DTC

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

### Action Taken When the DTC Sets

• | The TCM will request the illumination of the hold lamp and store the DTC when the TCM detects a failure on the 1st ignition cycle

• | The TCM judges the throttle opening is 0 percent for shift point and lock-up point control.

• | The TCM judges the throttle opening is 100 percent for line pressure control.

• | No lock-up

• | No self-learning control

• | The 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

• | The ECM

• | The TCM

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Automatic Transmission? | -- | Go to Step 2 | Go to Diagnostic System Check - Automatic Transmission
2 |

1. Turn OFF the ignition.
2. Install the scan tool.
3. With the engine OFF, turn the ignition switch to the ON position.
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 1 vehicle drive cycle.

Is the hold lamp ON?

--

Go to Step 3

Go to Step 7

3 |

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 4

Go to Step 7

4 |

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 K14, or B14, or 88 of the ECM wiring connector.
4. Measure the resistance between terminal A7 of the TCM wiring connector and terminal K15, or B30, or 57 of the ECM wiring connector.

Is the resistance within the specified values?

0 Ω

Go to Step 5

Go to Step 6

5 |

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 6

Go to Step 8

6 | Repair the malfunctioning terminals as necessary. Did you complete the repair? | -- | System OK | --
7 | Repair the temporary connection failure of the connector. Did you complete the repair? | -- | System OK | --
8 |

1. Replace the TCM. Refer to Transmission Control Module Replacement .
2. Turn OFF the ignition.
3. Turn ON the ignition.
4. Verify if DTC U2105 is set.

Is the DTC set?

--

Go to Step 9

Go to Step 10

9 | Replace the ECM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 10 | --
10 |

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