For 1990-2009 cars
ABS Components
Cell 44: ABS/TCS Switch, Isolation Valve Solenoids, and PCM
Handling ESD Sensitive Parts Notice
Cell 50: Serial Data UART
Cell 14: G102, G104, G106, G110, and G301 (Battery Ground)

### Circuit Description

The PCM provides the EBTCM with information on engine torque output via a high speed, pulse width modulated (PWM) signal on CKT 464.

The information enables the EBTCM to determine if engine torque management is required during a traction control event.

### Conditions for Setting the DTC

The DTC C1277 will set if the EBTCM determines that there is a signal/circuit malfunction in CKT 464.

### Action Taken When the DTC Sets

The following actions are taken when the DTC sets:

• | A malfunction DTC is stored

• | The TCS is disabled

• | The TRACTION OFF indicator lamp is turned ON

### Conditions for Clearing the DTC

The DTC will clear under following conditions:

• | Conditions for the malfunction are no longer present. Use the scan tool clear DTCs function.

• | 100 ignition switch key cycles have passed without detecting any malfunctions

### Diagnostic Aids

Perform a thorough inspection of the wiring and the connectors.

Failure to carefully inspect wiring may result in a misdiagnosis. A misdiagnosis may result in replacing parts without repairing the malfunction.

Thoroughly inspect the following grounds:

• | G101

• | G102

• | G106

• | G110

The following condition can cause DTC C1277 set:

• | An open in CKT 464.

• | A short to ground in CKT 464.

• | A short to voltage in CKT 464.

• | Damaged wiring or connections.

• | Poor terminal contact.

If no circuit problem caused the DTC, perform a road test and monitor CKT 464 at the PCM when the DTC sets.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the ABS Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS
2 |

1. Turn OFF the ignition.
2. Disconnect the PCM harness connector.
3. Turn ON the ignition leaving the engine OFF.
4. Use the J 39200 in order to measure the voltage between the PCM harness connector C2 terminal 9 (Buick) or connector C2 terminal 27 (Oldsmobile) and ground.

Is the voltage within the specified range?

Battery Voltage

Go to Step 3

Go to Step 4

3 |

1. Turn OFF the ignition.
2. Reconnect the PCM harness connector.
3. Turn ON the ignition leaving the engine OFF.
4. Use the appropriate adapter and the J 39200 in order to backprobe between the PCM connector C2 terminal 9 (Buick) or connector C2 terminal 27 (Oldsmobile) and ground.

Is the voltage within the specified range?

0.75-2.5 V

Go to Step 12

Go to Step 8

4 |

1. Turn OFF the ignition.
2. Disconnect the EBTCM connector.
3. Use the J 39200 in order to measure the resistance from the PCM connector C2 terminal 9 (Buick) or connector C2 terminal 27 (Oldsmobile) to ground.

Is the resistance less than the specified value?

OL (Infinite)

Go to Step 5

Go to Step 6

5 | Repair the short to ground in CKT 464. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
6 |

1. Connect the J 38716 pinout box to the EBTCM connector.
2. Use the J 39200 in order to measure resistance from the J 38716 terminal 6 to the PCM connector C2 terminal 9 (Buick) or connector C2 terminal 27 (Oldsmobile).

Is the resistance less than the specified value?

2 ohms

Go to Step 13

Go to Step 7

7 | Repair the open or high resistance in CKT 464. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
8 | Use the J 39200 in order to measure the voltage from the PCM connector C1 terminal 9 (Buick) or connector C2 terminal 27 (Oldsmobile) to ground. Is the voltage greater than the specified value? | 0.75 V | Go to Step 10 | Go to Step 9
9 | Repair the short to ground in CKT 464. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
10 | Inspect the PCM connector for poor terminal contact or damage. Did you find and correct the concern? | -- | Go to Diagnostic System Check - ABS | Go to Step 11
11 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls - 3.8L or Powertrain Control Module Replacement/Programming in Engine Controls - 4.0. Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --
12 | Is the DTC set as current? | -- | Go to Step 13 | Go to Diagnostic Aids
13 | Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check - ABS | --