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

### Circuit Description

When the EBTCM detects excessive wheel spin, the EBTCM will request that the PCM reduce engine torque via a high speed pulse width modulated (PWM) signal on CKT 463.

### Conditions for Setting the DTC

The DTC C1278 sets when the EBTCM receives a communication failure data message from the PCM.

The DTC C1278 sets under the two following conditions:

• | EBTCM to PCM communications. CKT 463 or CKT 800 is open or shorted

• | PCM driveability conditions that would set PCM DTCs. If PCM DTCs are present, the malfunction may not exist with the ABS/TCS system. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 4.0L.

### 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 be cleared 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 with no malfunctions detected.

### Diagnostic Aids

Perform a thorough inspection of the wiring and the connectors.

Failure to carefully inspect wiring may result in misdiagnosis. A misdiagnosis may result in part replacement with reappearance of the malfunction.

Thoroughly inspect the following grounds:

• | G101

• | G102

• | G106

• | G110

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check
2 | Use the scan tool in order to test for PCM DTC P1571 or any other PCM DTCs. Are there any PCM DTCs? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls-3.8L or Powertrain On Board Diagnostic (OBD) System Check in Engine Controls-4.0L | Go to Step 3
3 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the EBTCM harness connector.
3. Install the J 38716 pinout box.
4. Use the J 39200 digital multimeter (DMM) in order to measure the resistance between the J 38716 pinout box terminal 1 and the ground.

Is the resistance less than the specified value?

2 ohms

Go to Step 4

Go to Step 10

4 |

1. Turn the ignition switch to the RUN position.
2. Use the J 39200 in order to measure the voltage between the J 38716 pinout box terminal 1 and terminal 24.

Is the voltage within the specified range?

4.5-5.5 V

Go to Step 5

Go to Step 6

5 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the PCM harness connector.
3. Turn the ignition switch to the RUN position.
4. Use the J 39200 DMM in order to measure the voltage between the J 38716 pinout box terminal 1 and terminal 24.

Is the voltage less than the specified value?

1 V

Go to Step 14

Go to Step 11

6 | Use the J 39200 DMM in order to measure the resistance between the J 38716 pinout box terminal 1 and terminal 24. Is the resistance equal to the specified value? | OL (Infinite) | Go to Step 7 | Go to Step 12
7 | Use the J 39200 DMM in order to measure the resistance between the J 38716 pinout box terminal 24 and the PCM harness connector C1 terminal 71 (Buick) or connector C2 terminal 46 (Oldsmobile). Is the resistance within the specified range? | 0-2 ohms | Go to Step 8 | Go to Step 13
8 |

• | Inspect the following components:

- | The EBTCM connector

- | The EBTCM harness connector

- | The PCM connectors

- | The wiring

• | Inspect the above components for the following conditions:

- | Signs of terminal damage

- | Poor terminal contact

- | Terminal corrosion

Are there signs of poor terminal contact, corrosion, or damage in any of the components?

--

Go to Step 9

Go to Step 14

9 | Repair or replace any terminals, connectors and/or wiring that exhibit signs of poor terminal contact, corrosion, or damaged terminals. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
10 | Repair the open or high resistance in CKT 1451. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
11 | Repair the short to the voltage in CKT 463. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
12 | Repair the short to the ground in CKT 463. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
13 | Repair the open or high resistance in CKT 463. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | --
14 | Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | --