GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Grand Am 🢒 DTC 🢒 DTC C1252 LF ABS Channel in Release Too Long

Object Number: 189071 Size: SF
ABS Components
Antilock Brake System Schematics

Circuit Description

DTC C1252 diagnoses an ABS motor that energizes longer than expected. The following conditions may cause the longer period of being energized:

    • A wheel speed sensor malfunctions.
    • The left front brake solenoid valve mechanically fails open.
    • The ABS brake motor wires are crossed.

Conditions for Setting the DTC

DTC C1252 can only set during an ABS stop.

A malfunction exists if the EBCM commands the left front ABS channel in release for greater than three seconds.

Action Taken When the DTC Sets
    • A malfunction DTC stores.
    • The ABS disables.
    • The ABS warning indicator turns ON.
    • A rehome is commanded to ensure the motors are in the home position.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
    • 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

Diagnostic Aids

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. DTC C1252 may occur if the vehicle is on ice and the steering wheel is turned to lock during braking. Use the scan tool hydraulic test to ensure the total brake system is functional.

Thoroughly inspect any circuitry that may be causing the intermittent complaint for the following conditions:

    • Backed out terminals
    • Improper mating
    • Broken locks
    • Improperly formed or damaged terminals
    • Poor terminal-to-wiring connections
    • Physical damage to the wiring harness

Clear the DTCs after completing the diagnosis. Test drive the vehicle for three drive cycles in order to verify that the DTC does not reset. Use the following procedure in order to complete one drive cycle:

  1. Start the vehicle.
  2. Drive the vehicle over 16 km/h (10 mph).
  3. Stop the vehicle.
  4. Turn the ignition switch to the OFF position.

Test Description

  1. This test identifies a motor or hydraulic modulator malfunction.

    2.

  2. This test checks for a solenoid that may have mechanically failed open.

    3.

  3. This test checks for a solenoid that may have mechanically failed closed.

    4.

  4. This test isolates the malfunction to either the solenoid or the hydraulic modulator.

    5.

  5. This test checks for proper operation of the hydraulic modulator.

Step

Action

Value(s)

Yes

No

Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.

Important: Inspect for and correct the following conditions in the base brake or suspension system before proceeding with the DTC diagnosis:

   • Excessive drag
   • High resistance

1

Was the ABS Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Turn the ignition switch to the ON position.

    2. Do not start the engine.

  2. Install a Scan Tool .
  3. Use the Scan Tool in order to read the DTCs.

Are there any wheel speed sensor DTCs that set as current DTCs?

--

Go to the appropriate DTC table

Go to Step 3

3
  1. Select Data Display on the Scan Tool .
  2. Drive the vehicle, slowly decelerating from 56 km/h to 0 km/h (35 mph to 0 mph).

    3. Monitor all of the wheel speed sensor speeds while driving.

Do any of the wheel speed sensors indicate erratic or intermittent operation?

--

Go to the Excessive Wheel Speed Sensor Variation DTC for the affected wheel

Go to Step 4

4

  1. Turn the ignition switch to the ON position.

    2. Do not start the engine.

  2. Select Special Functions on the Scan Tool .
  3. Select the Manual Control function on the Scan Tool .
  4. Select the left front ABS Motor Apply function on the Scan Tool .
  5. Use the Scan Tool in order to apply the left front ABS motor.
  6. Apply firm pressure to the brake pedal.
  7. Select the left front ABS Motor Release function on the Scan Tool .
  8. Use the Scan Tool in order to release the left front ABS motor.

Did the brake pedal fall?

--

Go to Step 5

Go to Step 8

5

  1. Without exiting the Manual Control function on the scan tool, remove the firm pressure from the brake pedal.
  2. Select the left front ABS Brake Solenoid Valve on the Scan Tool .
  3. Use the Scan Tool in order to command the left front ABS brake solenoid valve ON.
  4. Apply firm pressure to the brake pedal.

Does the brake pedal fall?

--

Go to Step 7

Go to Step 6

6

  1. Continue to apply firm pressure to the brake pedal.
  2. Use the Scan Tool in order to command the left front ABS brake solenoid valve OFF.

Did the brake pedal fall?

--

Go to Step 14

Go to Step 7

7

  1. Remove the firm pressure from the brake pedal.
  2. Turn the ignition switch to the OFF position.
  3. Remove the left front ABS brake solenoid valve. Refer to Brake Solenoid Valve Replacement .
  4. Remove the right front ABS brake solenoid valve. Refer to Brake Solenoid Valve Replacement .
  5. Reinstall the left front ABS brake solenoid valve to the right front ABS brake solenoid valve position.
  6. Reinstall the right front ABS brake solenoid valve to the left front ABS brake solenoid valve position.
  7. Turn the ignition switch to the ON position.
  8. Make sure that the engine is OFF.
  9. Select the Manual Control function on the Scan Tool .
  10. Select the left front ABS Brake Solenoid Valve on the Scan Tool .
  11. Use the Scan Tool in order to command the left front ABS brake solenoid valve ON.
  12. Apply firm pressure to the brake pedal.

Does the brake pedal fall?

--

Go to Step 10

Go to Step 11

8

Did the brake pedal rise?

--

Go to Step 12

Go to Step 9

9

  1. Use the Scan Tool in order to perform the Gear Tension Relief function.
  2. Turn the ignition switch to the OFF position.
  3. Separate the ABS motor pack from the ABS brake modulator. Refer to ABS Motor Pack Replacement .
  4. Grasp the ABS brake modulator left front gear.

    5. (The ABS brake modulator left front gear is the large gear that is the closest to the front when the ABS brake modulator is mounted in the vehicle.)

  5. Attempt to rotate the ABS brake modulator left front gear in either direction.

Is it possible to rotate the ABS brake modulator left front gear by hand?

--

Go to Step 13

Go to Step 10

10

Replace the ABS brake modulator. Refer to Brake Pressure Modulator Valve Assembly Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

11

Replace the ABS brake solenoid valve that was originally in the left front ABS brake solenoid valve position. Refer to Brake Solenoid Valve Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

12

Repair the crossed wires to the left front ABS motor (CKT 1280 and CKT 1281).

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

13

Replace the ABS brake motor pack. Refer to ABS Motor Pack Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

14

The malfunction is intermittent or is not present at this time.

Refer to Diagnostic Aids for more information.

Is the action complete?

--

System OK

--