GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1238

Circuit Description

The EBCM monitors vehicle speed deceleration, system activation, and stoplamp switch active times in order to calculate an estimate of the brake rotor temperatures. If the EBCM calculates that the brake rotor temperatures have exceeded the thermal cutoff point, the EBCM will temporarily suspend the TCS function until the brake rotors cool. This feature is used to maintain braking effectiveness if normal base braking is required. An overly heated brake system could result in brake fade.

The EBCM continues calculating the brake rotor temperatures after the ignition is turned OFF. The EBCM remains awake until the EBCM calculates that the brake rotors cooled sufficiently. The cooling period may take up to 30 minutes.

Conditions for Running the DTC

The ABS conditions and the braking conditions are normal.

Conditions for Setting the DTC

This DTC sets when the estimated brake rotor temperature of either of the drive wheels exceeds 375°C (700°F). When the estimated brake rotor temperature of either of the drive wheels exceeds 375°C (700°F) during normal braking or normal ABS operations, the DTC does not set until the next TCS activation. The brake rotor temperature can exceed 375°C (700°F) without setting the DTC if a TCS activation has not occurred. When the estimated brake rotor temperature of either of the drive wheels exceeds 375°C (700°F) during a TCS activation, the DTC sets immediately, but the EBCM does not disable TCS until the end of the TCS event.

Action Taken When the DTC Sets
    • The EBCM disables the TCS until the DTC becomes a history DTC.
    • The DIC displays the Traction Suspended message.
    • The ABS remains functional.

Conditions for Clearing the DTC
    • The current DTC becomes history when the estimated brake rotor temperatures of both drive wheels decreases below 275°C (530°F). The following actions also occur:
       - The EBCM enables TCS.
       - The DIC displays the Traction Ready message.
    • The condition for the DTC is no longer present (the DTC is not current) and you used the scan tool Clear DTC function.
    • The condition for the DTC is no longer present (the DTC is not current) and you used the On-Board Diagnostics Clear DTC function.
    • The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids
    • With TCS temporarily disabled, the EBCM continues calculating the brake rotor temperatures after the ignition is turned OFF. Turning ON the ignition again while TCS is temporarily disabled will not re-enable TCS.
    • The temperature is an estimate calculated by the EBCM.
    • Possible causes of this DTC are the following conditions:
       - The brake usage is excessive.
       - The TCS usage is excessive.
       - The stoplamp switch is misaligned or damaged.

Test Description

The number below refers to the step number on the diagnostic table.

  1. Use the scan tool in order to verify that the Brake Thermal Model is exceeded.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the display DTCs function on the scan tool for the EBCM.

Does the scan tool display that this DTC is set current?

Go to Step 4

Go to Step 3

3

Since most occurrences of this DTC are caused by excessive braking, review with the customer to verify the conditions under which the DTC set.

Did vehicle operation cause this DTC to set?

Go to Diagnostic Aids

Go to Step 4

4

  1. Allow 30 minutes from the last time you drove the vehicle for the cooling of the brake rotors.
  2. With a scan tool, observe the Brake Temp Status parameter in the DRP/ABS/TCS data list.

Does the scan tool display Normal?

Go to Step 6

Go to Step 5

5

Inspect the alignment of the stoplamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Did you find and correct the condition?

Go to Step 8

Go to Step 6

6
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset as a current DTC?

Go to Step 7

System OK

7

Important: Perform the setup procedure for the EBCM. An unprogrammed EBCM will result in the following conditions:

   • Inoperative or poorly functioning system operations
   • The EBCM sets DTC C1248 and DTC C1255m3

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the repair?

Go to Step 8

--

8
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK