Circuit Description
The class 2 serial data line allows all of the modules on the line to transmit information to each other as needed. Each module is assigned an ID. All of the information sent out on the line is assigned a priority by which it is received. When the ignition is turned ON, each module begins to send and receive information. Each module on the class 2 serial data line knows what information the module needs to send out and what information the module should be receiving. What the modules do not know is which module is supposed to send the information. This information is only learned after the module has received the information needed along with the ID of the module that sent the information. This information is then remembered until the ignition switch is turned off.
Conditions for Setting the DTC
| • | The ignition is ON. |
| • | The PCM does not receive any messages from the EBTCM for 7 seconds. |
Action Taken When the DTC Sets
| • | A malfunction DTC is stored. |
| • | The TCS is disabled. |
| • | The TRACTION CONTROL indicator is turned ON. |
| • | The ABS remains functional. |
Conditions for Clearing the DTC
| • | The condition for DTC is no longer present and you used scan tool Clear DTCs function. |
| • | The condition for DTC is no longer present and you used the On-Board Clear DTCs function. |
| • | The EBTCM does not detect the DTC in 50 drive cycles. |
Diagnostic Aids
| • | Thoroughly inspect the wiring and the connectors. Failure to carefully and fully inspect the wiring and the connectors may result in misdiagnosis. Misdiagnosis may cause part replacement without repairing the malfunction. |
| • | The following conditions may cause an intermittent malfunction: |
| - | A poor connection |
| - | Rubbed through wire insulation |
| - | A wire broken inside the insulation |
| • | The following conditions are other possible causes for this malfunction: |
| - | A serial data class 2 transmit fault on the EBTCM |
| - | A serial data class 2 receiver fault on the PCM |
| - | Extreme serial data class 2 bus traffic |
| - | A wiring problem, terminal corrosion, or a poor connection in the CKT 1807 |
| • | If an intermittent malfunction exists, refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks to see if the PCM is sending the proper power mode position message.
-
This step checks to see if the EBTCM is sending out the required information on the serial data class 2.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |||||||||
2 | Inspect the following grounds, ensuring that each ground is clean, tight, free of damage, and torqued to the proper specifications:
Were any loose, damaged, or corroded grounds found? | -- | Go to Step 3 | Go to Step 4 | ||||||||
3 | Repair the grounds as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||
4 |
Is DTC U1016 or U1255 present? | -- | Go to Step 5 | |||||||||
5 |
Does the scan tool read the proper power mode position? | -- | Go to Step 6 | |||||||||
6 | Use a scan tool in the Applications menu in order to read the Class 2 Normal Mode Message Monitor. Is the EBTCM sending a Class 2 normal mode message? | -- | Go to Step 7 | Go to Step 8 | ||||||||
7 | Suspect the PCM. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 4.0L, 4.6L. Did you complete the diagnosis? | -- | -- | |||||||||
8 | Replace the EBTCM. Refer to Electronic Brake Control Module Replacement . Did you complete the repair? | -- | -- |
