DTC C1277 Requested Torque Signal Circuit Malfunction Rear Mounted EBTCM/BPMV
Circuit Description
Traction Control is simultaneously controlled by the EBTCM and the PCM. The PCM receives a REQUESTED TORQUE request via a Pulse Width Modulated (PWM) signal from the EBTCM requesting the desired torque level for proper Traction Control system 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 PCM or there is a TCS communication malfunction detected by the PCM and indicated to the EBTCM, by broadcasting a PWM message.
Action Taken When the DTC Sets
TCS is disabled.
| • | Indicators that turn on: |
| Car Icon (TCS indicator) |
| • | Messages displayed on the DIC: |
| Service Traction System |
Conditions for Clearing the DTC
| • | Condition for DTC is no longer present and scan tool clear DTC function is used. |
| • | Fifty ignition cycles have passed with no DTCs detected. |
Diagnostic Aids
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. |
| • | If an intermittent malfunction exists refer to Testing for Electrical Intermittents in Wiring Systems. |
| • | Possible causes for DTC C1277 to set: |
| - | Open in CKT 463. |
| - | CKT 463 shorted to ground or voltage. |
| - | Communication frequency problem. |
| - | Communication duty cycle problem. |
| - | CKT 463 has a wiring problem, terminal corrosion, or poor connections. |
| - | PCM not receiving information from EBTCM. |
Test Description
The numbers below refer to step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 | Check the following grounds, G402 and G106 making sure each ground is clean tight and free of damage. Refer to Ground Distribution Schematics in Wiring Systems. Were any loose, damaged, or corroded grounds found? | -- | ||
3 | Repair ground as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
Is the duty cycle within the range specified in the value(s) column? | 85-95 % | |||
Using J 39200 DMM, measure the DC Hz between J 39700 terminals 25 and B. Is the frequency within the range specified in the value(s) column? | 121-134 Hz | |||
6 |
Is the voltage within the range specified in the value(s) column? | 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 within the range specified in the value(s) column? | Greater than 1 V | ||
9 | Repair CKT 463 for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
10 |
Is the resistance within the range specified in the value(s) column? | OL (infinite) | ||
11 | Repair CKT 463 for a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
12 | Using J 39200 DMM, measure the resistance between terminal 25 of J 39700 and the PCM connector C1 terminal 46. Is the resistance within the range specified in the value(s) column? | 0-2 ohms | ||
13 | Replace the PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement in Engine Controls. Is the diagnosis complete? | -- | Go to Diagnostic System Check | -- |
14 | Repair CKT 463 for an open. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
DTC C1277 Requested Torque Signal Circuit Malfunction Front Mounted EBTCM/BPMV
Circuit Description
Traction Control is simultaneously controlled by the EBTCM and the PCM. The PCM receives a REQUESTED TORQUE request via a Pulse Width Modulated (PWM) signal from the EBTCM requesting the desired torque level for proper Traction Control system 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 PCM or there is a TCS communication malfunction detected by the PCM and indicated to the EBTCM, by broadcasting a PWM message.
Action Taken When the DTC Sets
TCS/Active Handling (if equipped with RPO JL4) are disabled.
| • | Indicators that turn on: |
| Car Icon (TCS indicator) |
| • | Messages displayed on the DIC: |
| Service Traction System |
| Service Active HNDLG (if equipped with RPO JL4) |
Conditions for Clearing the DTC
| • | Condition for DTC is no longer present and scan tool clear DTC function is used. |
| • | Fifty ignition cycles have passed with no DTCs detected. |
Diagnostic Aids
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction. |
| • | If an intermittent malfunction exists refer to Testing for Electrical Intermittents in Wiring Systems. |
| • | Possible causes for DTC C1277 to set: |
| - | Open in CKT 463. |
| - | CKT 463 shorted to ground or voltage. |
| - | Communication frequency problem. |
| - | Communication duty cycle problem. |
| - | CKT 463 has a wiring problem, terminal corrosion, or poor connections. |
| - | PCM not receiving information from EBTCM. |
Test Description
The numbers below refer to step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 | Check the following grounds, G101 and G106 making sure each ground is clean tight and free of damage. Refer to Ground Distribution Schematics in Wiring Systems. Were any loose, damaged, or corroded grounds found? | -- | ||
3 | Repair ground as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
Is the duty cycle within the range specified in the value(s) column? | 85-95 % | |||
Using J 39200 DMM, measure the DC Hz between J 39700 terminals 25 and B. Is the frequency within the range specified in the value(s) column? | 121-134 Hz | |||
6 |
Is the voltage within the range specified in the value(s) column? | 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 within the range specified in the value(s) column? | Greater than 1 V | ||
9 | Repair CKT 463 for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
10 |
Is the resistance within the range specified in the value(s) column? | OL (infinite) | ||
11 | Repair CKT 463 for a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
12 | Using J 39200 DMM, measure the resistance between terminal 25 of J 39700 and the PCM connector C1 terminal 46. Is the resistance within the range specified in the value(s) column? | 0-2 ohms | ||
13 | Replace the PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement in Engine Controls. Is the diagnosis complete? | -- | Go to Diagnostic System Check | -- |
14 | Repair CKT 463 for an open. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
