For 1990-2009 cars
ABS Components
Cell 44: ABS/TCS Switch, UART, PCM, and Traction Control Switch
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Antilock Brake System Connector End Views

### Circuit Description

The 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 EBTCM requesting the desired torque level for proper 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 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 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 Intermittents and Poor Connections Diagnosis in Wiring Systems

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step checks for the proper duty cycle.

2. This step checks for the proper frequency.

#### DTC C1277 Requested Torque Signal Circuit Malfunction

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check
2 | Check the following grounds, G101, and G106 making sure each ground is clean tight and free of damage. 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. Is the repair complete? | -- | Go to Diagnostic System Check | --
4 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the EBTCM connector.
3. Install the J 39700 universal pinout box using the J 39700-25 cable adapter to the EBTCM harness connector and the EBTCM connector.
4. Turn the ignition switch to the RUN position with the engine off.
5. Using the J 39200 DMM, measure the DC duty cycle between the J 39700 terminals 1 and B.

Is the duty cycle within the specified range?

85-95%

Go to Step 5

Go to Step 6

5 | Using the J 39200 , measure the DC Hz between the J 39700 terminals 1 and B. Is the frequency within the specified range? | 121-134 Hz | Go to Step 13 | Go to Step 7
6 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the J 39700-25 cable adapter from the EBTCM, leaving the J 39700 connected to the EBTCM harness only.
3. Using the J 39200 DMM, measure the voltage between the J 39700 terminals 1 and B.

Is the voltage within the specified range?

4.5-5.5 V

Go to Step 7

Go to Step 8

7 | Replace the EBTCM. Refer to Electronic Brake Control Module Replacement . Is the replacement complete? | -- | Go to Diagnostic System Check | --
8 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the PCM connector C1.
3. Turn the ignition switch to the RUN position with the engine off.
4. Using the J 39200 DMM, measure the voltage between the J 39700 terminals 1 and B.

Is the voltage greater than the specified value?

1.0 V

Go to Step 9

Go to Step 10

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 |

1. Turn the ignition switch to the OFF position.
2. Using the J 39200 DMM, measure the resistance between the J 39700 terminals 1 and B.

Is the resistance equal tot eh specified value?

OL (infinite)

Go to Step 12

Go to Step 11

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 1 and the PCM connector C1 terminal 71. Is the resistance less than the specified value? | 2 ohms | Go to Step 13 | Go to Step 14
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 | --