For 1990-2009 cars
Data Link Communications Components
Cell 50 EBTCM and TCM CAN Interface

### Circuit Description

The Controller Area Network (CAN) serial data circuit is a high speed serial data bus used to communicate information between the Electronic Brake and Traction Control Module (EBTCM), the Engine Control Module (ECM) and the Transmission Control Module (TCM). When the ignition switch is turned to the ON position, the modules begin to transmit data between each other. The following data is transmitted and received between the ECM and TCM:

• | Brake Switch signal from the ECM to the TCM

• | Throttle Position Angle from the ECM to the TCM

• | Engine Speed signal from the ECM to the TCM

• | Engine Coolant Temperature from the ECM to the TCM

• | Engine Torque signal from the ECM to the TCM

• | MIL Request signal from the TCM to the ECM

The following data is transmitted and received between the ECM and EBTCM:

• | Requested Torque from the EBTCM to the ECM

• | Delivered Torque from the ECM to the EBTCM

• | Engine Speed (RPM) from the ECM to the EBTCM

The addressing scheme employed with CAN assigns a label to every message, with each message receiving a unique "identifier". The identifier classifies the content of the message (such as engine speed). Each module processes only those messages whose identifiers are stored in the module's acceptance list. This is CAN's form of message filtering.

The identifier labels both the data content and the priority of the message being sent. Each module can begin transmitting its most important data as soon as the bus is unoccupied. When more than one module starts to transmit simultaneously, the message with the highest priority is assigned first access. A module responds to failure to gain access by automatically switching to receive mode, the module then repeats the transmission attempt as soon as the bus is free again.

### Conditions for Running the DTC

The CAN Bus circuit is monitored continuously after the ignition switch is turned to the ON position.

### Conditions for Setting the DTC

Each controller on the CAN Bus has a reset counter that keeps track of how many times the controller re-initializes communications on the bus. The maximum allowable is 7. The control module that has set the DTC has attempted to re-initialize communication on the CAN Bus 7 times with no success.

### Action Taken When the DTC Sets

The following describes the action taken when the code is set in a particular control module.

#### Engine Control Module

• | The Malfunction Indicator Lamp (MIL) is illuminated on the second consecutive drive trip that the diagnostic runs and fails.

• | The ECM records the operating conditions at the time the MIL is illuminated in the Freeze Frame.

#### Transmission Control Module

• | The Service Transmission Lamp (STL) is illuminated.

• | The TCM sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.

• | The transmission operates in the Default Mode:

- | Maximum line pressure

- | Command 4th gear

- | Inhibit TCC

- | Freeze shift adapts

#### Electronic Brake Traction Control Module

• | A malfunction DTC is stored.

• | TCS is disabled.

• | The TC indicator is illuminated.

### Conditions for Clearing the MIL/DTC

The following describes the conditions for clearing the MIL/DTC in a particular control module.

#### Engine Control Module

• | The condition for the DTC is no longer present. The ECM turns off the MIL after 3 consecutive drive trips that the diagnostic runs and passes.

• | The scan tool clear DTC function is used.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.

• | The ECM battery voltage is interrupted.

#### Transmission Control Module

• | The condition for the DTC is no longer present. The TCM turns off the STL.

• | The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.

• | The scan tool clear DTC function is used.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.

• | The TCM cancels the DTC Default Mode actions when the malfunction no longer is present and the ignition switch is off long enough to power down the TCM.

#### Electronic Brake Traction Control Module

• | The condition for the DTC is no longer present.

• | The scan tool clear DTC function is used.

• | A history DTC clears after 100 ignition cycles pass with no malfunction detected.

### Diagnostic Aids

This DTC is confined to a malfunction with the control module that the DTC was set in, or the control module(s) that is connected to the module the code was set in. A physical malfunction of the harness is not the cause of this DTC. If there is a malfunction with the CAN Bus harness, DTC U2100 will be set.

The scan tool can be used as an aid in diagnosing this DTC. In the scan tool data display, observe the following parameters that are transmitted over the CAN Bus:

#### Engine Data Display

MIL Request

#### Transmission Data Display

• | Brake Switch

• | Engine Coolant Temperature (ECT)

• | Engine Speed

• | Engine Torque

• | Throttle Position (TP) Angle

#### ABS Data Display

• | Engine Speed

• | Delivered Engine Torque

Observing the data display parameters for abnormalities or missing data may pinpoint which control module is causing the malfunction.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. A DTC U2100 set in either the ECM, TCM or EBTCM may have caused U2104 to set. You must diagnose and clear DTC U2100 to determine if it is the cause of U2104 setting.

2. A U2105, U2106 or U2108 DTC with a history status may indicate the cause of U2104.

3. The module(s) which are not communicating data is the likely cause of U2104 being set.

4. The module(s) which was not communicating data due to a poor connection to the CAN Bus circuit may have set other CAN Bus codes for the bus or modules that it was monitoring.

5. The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

6. If all modules are communicating, the module which set U2104 may have done so due to some other condition.

7. The module which set U2104 is the likely cause of the malfunction.

#### DTC U2104 CAN BUS Reset Counter Overrun

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Data Link Communications Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check - Data Link Communications
2 | Was DTC U2100 recorded as a history or current DTC in the ECM, TCM or EBTCM? | -- | Go to DTC U2100 CAN-BUS Communication Malfunction and perform the diagnostics for the DTC | Go to Step 3
3 | Were any of the following DTCs recorded with a history status?

• | DTC U2105

• | DTC U2106

• | DTC U2108

--

Go to Diagnostic Trouble Code (DTC) List and perform the diagnostics for the applicable DTC

Go to Step 4

4 |

1. Turn the Ignition switch to the ON position, engine running.
2. Using the scan tool, observe the following data displays:

• | Engine Data Display

• | Transmission Data Display

• | ABS Data Display

3. Observe the data parameters listed in the Diagnostic Aids for missing data.

Is any module on the CAN Bus not receiving data?

--

Go to Step 5

Go to Step 12

5 |

1. Disconnect the connector from the module that set DTC U2104.
2. Inspect the connector for the following:

• | poor terminal contact

• | Corrosion

• | Damage

3. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 6

6 |

1. Disconnect the connector(s) from the module(s) that are not communicating data on the CAN Bus.
2. Inspect the connector(s) for the following:

• | poor terminal contact

• | Corrosion

• | Damage

3. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

7 | Replace the Module(s) which are not communicating data. Refer to Engine Control Module Replacement/Programming in Engine Controls 3.0L or Transmission Control Module Replacement in Automatic Transmission 4L30-E or Electronic Brake and Traction Control Module Replacement in Antilock Brake System.

Did you complete the replacement?

--

Go to Step 10

--

8 |

1. Reconnect all connectors.
2. Install a scan tool.
3. Turn the ignition switch to the ON position, engine off.
4. Select the Display DTCs function of the module(s) which was not communicating data.

Does the scan tool display any DTCs other than the following?

• | U2100

• | U2103

• | U2104

• | U2105

• | U2106

• | U2108

--

Go to the applicable DTC Table

Go to Step 9

9 | Clear DTCs using the Scan Tool Did you complete the action? | -- | Go to Step 10 | --
10 |

1. Install a scan tool if not previously installed.
2. Turn the ignition switch to the ON position.
3. Select the Display DTCs function of the module(s) which had U2104 set as a current DTC.

Does the scan tool display any DTCs other than the following?

• | U2100

• | U2103

• | U2104

• | U2105

• | U2106

• | U2108

--

Go to the applicable DTC Table

Go to Step 11

11 | Clear DTCs using the scan tool. Did you complete the action? | -- | System OK | --
12 | Did you record any other DTCs for the module(s) which had U2104 set as a current DTC? | -- | Go to the applicable DTC Table | Go to Step 13
13 |

1. Install a scan tool.
2. Turn the ignition switch to the ON position, engine off.
3. Clear DTCs using the scan tool.
4. Turn the ignition to the OFF position for at least 5 seconds.
5. Turn the ignition to the ON position, engine off.
6. Select the Display DTCs function.

Does the scan tool display DTC U2104 as a current DTC?

--

Go to Step 14

System OK

14 | Replace the module which had DTC U2104 set as a current DTC. Refer to Engine Control Module Replacement/Programming in Engine Controls 3.0L or Transmission Control Module Replacement in Automatic Transmission 4L30-E or Electronic Brake and Traction Control Module Replacement in Antilock Brake System.

Did you complete the replacement?

--

System OK

--