Circuit Description
The EBCM/EBTCM and the PCM simultaneously control the traction control. The PCM receives a Requested Torque message via a pulse width modulated (PWM) signal from the EBCM/EBTCM requesting the desired torque level for proper TCS operation. The PCM supplies the pull up voltage.
Conditions for Setting the DTC
The DTC sets if one of the following occur:
| • | An open or short in the Requested Torque line between the EBCM/EBTCM and the PCM. |
| • | A TCS communication malfunction detected by the PCM and indicated to the EBCM/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 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 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 CKT 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 Testing for Electrical Intermittents in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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 grounds as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
Is the duty cycle within the specified range? | 85-95% | |||
Using the J 39200 , measure the DC Hz between the J 39700 terminals 25 and B. Is the frequency within the specified range? | 121-134 Hz | |||
6 |
Is the voltage within the specified range? | 4.5-5.5 V | ||
7 | Replace the EBTCM. Refer to Electronic Brake Control Module Replacement . Is the replacement complete? | -- | Go to Diagnostic System Check | -- |
8 |
Is the voltage greater than the specified value? | 1.0 V | ||
9 | Repair the short to voltage in CKT 463. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
10 |
Is the resistance within specifications? | OL (infinite) | ||
11 | Repair the short to ground in CKT 463. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
12 | Using the J 39200 DMM, measure the resistance between the J 39700 terminal 25 and the PCM connector C1 terminal 71. Is the resistance less than the specified value? | 2 ohms | ||
13 | Suspect the PCM. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 3.8L. Is the diagnosis complete? | -- | Go to Diagnostic System Check | -- |
14 | Repair the open in CKT 463. Refer to Wiring Repairs in Wiring Systems. Is the circuit repair complete? | -- | Go to Diagnostic System Check | -- |
