C1277

CIRCUIT DESCRIPTION
The Electronic Brake and Traction Control Module (EBTCM) and the Powertrain Control Module (PCM) simultaneously control the traction control. The PCM receives a REQUESTED TORQUE message via a Pulse Width Modulated (PWM) signal from the EBTCM requesting the desired torque level for proper Traction Control System (TCS) operation. The PCM supplies the pull up voltage.

CONDITIONS FOR SETTING THE DTC
There is an open or short in the REQUESTED TORQUE line between the EBTCM and the PCM or there is a TCS communication malfunction detected by the PCM and indicated to the EBTCM via a PWM message

ACTION TAKEN WHEN THE DTC SETS
^ A DTC C1277 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 Diagnostic Trouble Code (DTC) is no longer present and the scan tool clear DTC function is used
^ 50 ignition cycles have passed with no DTCs detected

DIAGNOSTIC AIDS
^ Thoroughly inspect the wiring and the connectors. Failure to carefully and fully inspect the wiring and the connectors can result in misdiagnosis. Misdiagnosis causes reappearance of the malfunction with part replacement.
^ The following conditions are other possible causes for this malfunction.
- An open, a short to ground, or a short to voltage in CAT 463
- A communication frequency problem
- A communication duty cycle problem
- A wiring problem, terminal corrosion, or a poor connection in CKT 463
- The PCM is not receiving information from the EBTCM
^ If an intermittent malfunction exists, refer to Troubleshooting Procedures.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
4. This step checks for the proper duty cycle.
5. This step checks for the proper frequency.