For 1990-2009 cars
ABS Components
Antilock Brake System Schematics

### Circuit Description

DTC C1254 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 ABS motor does not turn.

• | The ABS brake motor wires cross.

### Conditions for Setting the DTC

• | DTC C1254 can only set during an ABS stop.

• | A malfunction exists if the EBCM commands the rear ABS channel in release for greater than three seconds.

### Action Taken When the DTC Sets

• | A malfunction DTC stores.

• | The ABS disables.

• | The amber ABS warning indicator(s) turn 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

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. Use the Scan Tool hydraulic test in order 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 to the OFF position.

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 brake drag

• | High resistance

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 ON position.

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 List 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 OFF position.
2. Raise and suitably support the rear of the vehicle. Make sure that the two rear wheels are off of the ground.

Refer to Lifting and Jacking the Vehicle in General Information.

3. Spin each of the rear wheels by hand.

Is it possible to spin each rear wheel freely by hand?

--

Go to Step 5

Go to Step 11

5 |

1. Turn the ignition switch to the ON position.

Do not start the engine.

2. Select the Manual Control function on the Scan Tool .
3. Select the Rear ABS Motor Apply function on the Scan Tool .
4. Apply firm pressure to the brake pedal.
5. Use the Scan Tool in order to apply the Rear ABS motor.
6. Spin each rear wheel by hand.

Is it possible to freely spin each rear wheel?

--

Go to Step 6

Go to Step 12

6 |

1. Continue to apply firm pressure to the brake pedal.
2. Use the Scan Tool in order to command a Motor Release of the rear ABS motor.

Is it possible to freely spin each rear wheel?

--

Go to Step 7

Go to Step 9

7 |

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, if it is disconnected.
4. Turn the ignition switch to the ON position.

Do not start the engine.

5. Use the Scan Tool in order to perform a ABS brake motor pack motor test.

Do all three of the ABS brake motor pack gears (small gears) spin freely when commanded?

--

Go to Step 8

Go to Step 10

8 | Replace the ABS brake modulator. Refer to Brake Modulator Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | --
9 | Repair the crossed wires to the rear ABS motor (CKT 6E01 and CKT 6F01). Is the repair complete? | -- | Go to Diagnostic System Check | --
10 | Replace the ABS brake motor pack. Refer to ABS Motor Pack Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | --
11 | Repair the source of resistance in the base brake system. Refer to the diagnostic procedures in Hydraulic Brakes. Is the repair complete? | -- | Go to Diagnostic System Check | --
12 | The malfunction is intermittent or is not present at this time. Refer to Diagnostic Aids for more information. Is the action complete? | -- | System OK | --