GM Service Manual Online
For 1990-2009 cars only

Object Number: 375185  Size: MF
ABS Components
Cell 44: ABS/TCS Switch, UART, PCM, and Traction Control Switch
Handling ESD Sensitive Parts Notice
Cell 50: UART Serial Data Line

Circuit Description

The PCM monitors various parameters and will not allow traction control operation if any parameter falls below a specified value.

Conditions for Setting the DTC

The PCM detects a malfunction and then causes TCS shut down until the malfunction has been corrected

Action Taken When the DTC Sets

    • A DTC C1278 is stored (This is a temporary malfunction)
    • The TCS is disabled
    • The TRACTION OFF indicator is turned on
    • If the TCS is no longer inhibited, the indicator will be turned off but the DTC will be stored

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

This code is for information only. As an aid to the technician, this code indicates that there are no problems in the ABS/TCS system

Test Description

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

  1. This step checks if DTC C1278 resets.

DTC C1278 TCS Temporarily Inhibited By PCM

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Turn the ignition switch to the RUN position with the engine off.
  2. Using a scan tool, read the ABS/TCS DTCs.

Are any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List for Appropriate DTC Table

Go to Step 3

3

Is DTC C1278 set as a current code?

--

Go to Step 5

Go to Step 4

4

  1. Start the engine and test drive the vehicle at least 16 km/h (10 mph) while monitoring the scan tool for ABS/TCS DTCs.
  2. Repeat the above drive cycle sequence two more times.
  3. Did DTC C1278 set in the last three drive cycles?

--

Go to Step  5

Go to Diagnostic System Check

5

Perform the Powertrain OBD System Check. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 3.8L.

Did the vehicle pass the OBD System Check?

--

Go to Diagnostic Aids

Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 3.8L