Circuit Description
The Class 2 serial data line allows all the modules on the line to transmit information to each other as needed. Each module is assigned an ID and all the information sent out on the line is assigned a priority by which it is received. When the ignition switch is turned to the RUN position each module begins to send and receive information. Each module on the Class 2 serial data line knows what information it needs to send out and what information it should be receiving. What the modules do not know is which module is supposed to send them the information. This information is only learned after the module has received the information it needs along with the ID of the module that sent the information. This information is then remembered until the ignition switch is turned off. If the EBTCM loses communication with the Powertrain Control Module (PCM) then DTC U1016 will be set by the EBTCM.
Conditions for Setting the DTC
The ignition switch is in the RUN position and the PCM does not communicate with the EBTCM for 7 seconds
Action Taken When the DTC Sets
| • | A DTC C1298 is stored |
| • | The TCS is disabled. |
| • | The TRACTION OFF indicator is turned on |
| • | The ABS remains functional |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and you used the scan tool Clear DTC function. |
| • | The EBCM/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 Class 2 transmit fault on the EBTCM |
| - | A Class 2 receiver fault on the PCM |
| - | Extreme Class 2 bus traffic |
| - | A wiring problem, terminal corrosion, or a poor connection in the CKT 1807 |
| • | If an intermittent malfunction exists, refer to Testing for Electrical Intermittents in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks to see if the SBM is sending the proper power mode position message.
-
This step checks to see if the EBTCM is sending out the required information on the Class 2 serial data line.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the ABS Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 | Check the following grounds, G101, and G104 making sure each ground is clean tight and free of damage. Were any loose, damaged, or corroded grounds found? | -- | ||
3 | Repair the ground(s) as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
4 |
Are any of the following DTCs present: U1016, or U1255? | -- | ||
5 |
Does the scan tool read the proper power mode position? | -- | Go to Diagnostic System Check | |
6 | Using a scan tool in the ABS/TCS Data Display 2 - Normal Mode, read the State of Health Present parameter. Does the scan tool display yes? | -- | ||
7 | Suspect the PCM. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls. Is the diagnosis complete? | -- | Go to Diagnostic System Check | -- |
8 | Replace the EBTCM. Refer to Electronic Brake Control Module Replacement . Is the replacement complete? | -- | Go to Diagnostic System Check | -- |
