GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Grand Am 🢒 DTC 🢒 DTC C1247 Left Front ABS Motor Free Spins

Object Number: 189071 Size: SF
ABS Components
Antilock Brake System Schematics
Handling ESD Sensitive Parts Notice

Circuit Description

DTC C1247 detects a stripped nut or gear assembly during initialization. During the homing sequence, the piston should reach the top of the bore resulting in a stalled ABS motor. If the ABS motor does not stall, the ABS motor must be spinning with little or no resistance. This indicates a nut/screw or gear malfunction.

Conditions for Setting the DTC

DTC C1247 can only set during initialization.

A malfunction exists if the feedback current is less than the command current for a specified period of time.

Action Taken When the DTC Sets
    • A malfunction DTC stores.
    • The ABS disables.
    • The ABS warning indicator turns ON.

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

The following conditions may cause an intermittent malfunction if the conditions exist in a mechanical part of the system:

    • Sticking
    • Binding
    • Slipping

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. DTC C1247 may set after modulator disassembly if the modulator pistons are positioned at the bottom of the modulator piston bore. If DTC C1247 only occurs once and DTC C1256 also occurs, refer to DTC C1256. If intermittent and enhanced diagnostics shows this DTC occurs during ABS, refer to DTC C1256.

Depending on the frequency of the malfunction, a physical inspection of the mechanical parts suspected of causing the malfunction may be necessary.

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 checks for motor movement by comparing the motor feedback current to the motor command current during apply.

    2.

  2. This test checks for motor movement by comparing the motor feedback current to the motor command current during release.

    3.

  3. This test checks for piston movement.

    4.

  4. This test checks for excessive resistance in the left front motor high circuit.

    5.

  5. This test checks for excessive resistance in the left front motor low circuit.

    6.

  6. This test checks for the proper left front motor resistance value.

    7.

  7. This test checks for proper operation of the motor pack.

    8.

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

    9.

  9. This test determines if the malfunction is caused by the EBCM.

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.

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. Use the Scan Tool in order to read the DTCs.

Does DTC C1256 also set as a current DTC?

--

Go to DTC C1256 Left Front ABS Motor Circuit Open

Go to Step 3

3

  1. Raise and suitably support the vehicle.

    2. Verify that the rear wheels are approximately 15 cm (6 in) above the floor.

    Refer to Lifting and Jacking the Vehicle in General Information.

  2. Pump the brake pedal until it is firm in order to deplete the brake booster vacuum reservoir.
  3. Install a Scan Tool .
  4. Apply firm downward pressure on the brake pedal.
  5. Select Special Functions on the Scan Tool .
  6. Select the Manual Control function on the Scan Tool .
  7. Select the ABS Motor Apply function on the Scan Tool .
  8. Use the Scan Tool to apply the left front motor.

    9. Observe the following currents:

    • The left front ABS motor command current
    • The left front ABS motor feedback current

Were the left front ABS motor command current and the left front ABS motor feedback current approximately the specified current?

10 A

Go to Step 4

Go to Step 6

4

  1. Apply firm pressure to the brake pedal.
  2. Select the left front ABS Motor Release function on the Scan Tool .
  3. Use the Scan Tool in order to release the left front ABS motor.

    4. Observe the following currents:

    • The left front ABS motor command current
    • The left front ABS motor feedback current

Have the following conditions been met?

    • The left front ABS motor command current and the left front ABS motor feedback current approximately the specified current
    • The brake pedal falls

6 A

Go to Step 5

Go to Step 6

5

  1. Continue to apply firm pressure to the brake pedal.
  2. Select the left front ABS Motor Apply function on the Scan Tool .
  3. Use the Scan Tool in order to apply the left front ABS motor.

Did the brake pedal rise?

--

Go to Step 22

Go to Step 6

6

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the ABS brake motor pack connector.
  3. Disconnect the EBCM connector
  4. Use the J 39200 in order to measure the resistance between the ABS brake motor pack connector terminal A and the EBCM connector terminal G.

Is the resistance within the specified value?

0-2 ohms

Go to Step 7

Go to Step 15

7

Use the J 39200 in order to measure the resistance between the ABS brake motor pack connector terminal B and the EBCM connector terminal H.

Is the resistance within the specified range?

0-2 ohms

Go to Step 8

Go to Step 16

8

Use the J 39200 in order to measure the resistance between the ABS brake motor pack connector terminal A and the ABS brake motor pack connector terminal B.

Is the resistance within the specified range?

0.2-1.5 ohms

Go to Step 9

Go to Step 17

9
  1. Perform the Gear Tension Relief function under Special Functions of the Scan Tool .
  2. Remove the ABS brake modulator assembly from the vehicle. Refer to Brake Pressure Modulator Valve Assembly Replacement .
  3. Remove the ABS brake modulator gear cover.
  4. Inspect for a stripped ABS brake motor pack left front gear.

    5. (The ABS brake motor pack is the unit with the three small gears. The ABS brake motor pack left front gear is the gear closest to the front when the ABS brake modulator is mounted in the vehicle.)

Is the ABS brake motor left front gear stripped?

--

Go to Step 17

Go to Step 10

10

Inspect for a stripped ABS brake modulator pack left front gear.

(The ABS brake modulator unit is the unit with the three large gears. The ABS brake modulator left front gear is the gear closest to the front when the ABS brake modulator is mounted in the vehicle.)

Is the ABS brake modulator left front gear stripped?

--

Go to Step 18

Go to Step 11

11

  1. Reconnect the ABS brake motor pack connector.
  2. Reconnect the EBCM connector.
  3. Carefully secure the ABS brake modulator into the vehicle.

    4. Secure the assembly in a position that permits observation of the gears.

  4. Turn the ignition switch to the ON position.

    5. Do not start the engine.

  5. Select the Manual Control function on the Scan Tool .
  6. Select the left front ABS Motor Apply function on the Scan Tool .
  7. Use the Scan Tool in order to apply the left front ABS motor while observing the ABS brake modulator left front gear set.

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

  8. Select the left front ABS Motor Release function on the Scan Tool .
  9. Use the Scan Tool in order to release the left front ABS motor while observing the ABS brake modulator left front gear set.
  10. Select the left front ABS Motor Apply function on the Scan Tool .
  11. Use the Scan Tool in order to apply the left front ABS motor while observing the ABS brake modulator left front gear set.

Does the ABS brake modulator left front gear set move at least one full revolution in both directions?

--

Go to Step 12

Go to Step 17

12

  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 brake motor pack from the ABS brake modulator. Refer to ABS Motor Pack Replacement .
  4. Grasp the ABS brake modulator left front gear.
  5. Rotate the ABS brake modulator left front gear.

Does the ABS brake modulator left front gear rotate more than 13 full turns from lock to lock?

--

Go to Step 19

Go to Step 13

13
  1. Disconnect the ABS brake motor pack connector.
  2. Disconnect the EBCM connector.
  3. Inspect the connectors for the following conditions:
    4. • Poor terminal contact
    • Corrosion

Do any of the terminals exhibit poor terminal contact or corrosion?

--

Go to Step 20

Go to Step 14

14

  1. Reinstall the ABS brake modulator gear cover.
  2. Reinstall the ABS brake modulator assembly in the vehicle.
  3. Reconnect the ABS brake motor pack connector.
  4. Reconnect the EBCM connector.
  5. Start the engine. Do not apply pressure to the brake pedal.
  6. Let the engine run for at least 10 seconds.
  7. Turn the ignition switch to the OFF position.
  8. Repeat the above cycle (step 5 through step 7) two more times.
  9. Use the Scan Tool in order to read the DTCs.

Does DTC C1247 set as a current DTC?

--

Go to Step 21

Go to Step 22

15

Repair the high resistance in CKT 1280. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

16

Repair the high resistance in CKT 1281. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

17

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

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

18

Replace the ABS brake modulator gear. Refer to Brake Modulator Gear Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

19

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

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

20

Replace the terminals that exhibit signs of poor terminal contact or corrosion. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

21

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

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

22

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

Refer to Diagnostic Aids for more information.

Is the action complete?

--

System OK

--