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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Corvette 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1277 Requested Torque Signal Circuit Malfunction

Object Number: 479932 Size: MF
Cell 44: Magnasteer System (JL4)
ABS Components
Antilock Brake System Schematic Icons

Circuit Description

The PCM monitors various parameters and will not allow Traction Control/Active Handling (if equipped with RPO JL4) operation if any parameter falls beyond a predetermined value.

Conditions for Setting the DTC

A malfunction has been detected by the PCM. The PCM then causes TCS/Active Handling shutdown until the malfunction has been corrected.

Action Taken When the DTC Sets

This is a temporary operational malfunction.

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

This code is for information only. It indicates there are no problems in the ABS/TCS/Active Handling system, is used as an aid to the technician.

Test Description

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

  1. Checks for proper duty cycle.

    2.

  2. Checks for 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 - ABS

2

Check the following grounds, G101 and G108 making sure each ground is clean tight and free of damage. Refer to Ground Ground Distribution Schematics EBTCM/BPMT in Wiring Systems.

Were any loose, damaged, or corroded grounds found?

--

Go to Step 3

Go to Step 4

3

Repair ground as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

4

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the EBTCM connector.
  3. Install 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 ON position, engine off.
  5. Using J 39200 DMM, measure the DC duty cycle between J 39700 terminals 25 and B.

Is the duty cycle within the range specified in the value(s) column?

85-95 %

Go to Step 5

Go to Step 6

5

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

Go to Step 13

Go to Step 7

6
  1. Turn the ignition switch to the OFF position.
  2. Disconnect J 39700-25 cable adapter from the EBTCM, leaving J 39700-25 cable adapter connected to the EBTCM harness connector only.
  3. Turn the ignition switch to the ON position, engine off.
  4. Using J 39200 DMM, measure the voltage between terminals 25 and B of J 39700 .

Is the voltage within the range specified in the value(s) column?

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 - ABS

--

8
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the PCM connector C1.
  3. Turn the ignition switch to the ON position engine off.
  4. Using J 39200 DMM, measure the voltage between terminals 25 and B of J 39700

Is the voltage within the range specified in the value(s) column?

Greater than 1 V

Go to Step 9

Go to Step 10

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 - ABS

--

10
  1. Turn the ignition switch to the OFF position.
  2. Using J 39200 DMM, measure the resistance between J 39700 terminals 25 and B.

Is the resistance within the range specified in the value(s) column?

OL (infinite)

Go to Step 12

Go to Step 11

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 - ABS

--

12

Using J 39200 DMM, measure the resistance between terminal 25 of J 39700 and the PCM connector C1 terminal 13.

Is the resistance within the range specified in the value(s) column?

0-2 ohms

Go to Step 13

Go to Step 14

13

Replace the PCM. Refer to PCM/TAC Module Replacement in Engine Controls.

Is the diagnosis complete?

--

Go to Diagnostic System Check - ABS

--

14

Repair CKT 463 for an open. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--