Motor Test

MOTOR TEST
Once the motor pack has been separated from the hydraulic modulator, this test will help determine if the motor pack is operating properly.

The scan tool will command the motors in one direction, then the other.
^ If any motor does not turn in both directions, the motor pack is malfunctioning and must be replaced. Refer to ABS Motor Pack Replacement under Hydraulic Assembly.
^ If all three motors rotate, try to rotate each gear on the hydraulic modulator.

NO GEAR MOVEMENT
After the motor pack has been removed, Rotate each gear by hand on the hydraulic modulator. the front gears (non-center gears) should be able to be rotated approximately 8.75 full turns, lock to lock.

If the gear does not turn freely or at least 8.5 turns are not possible, replace the hydraulic modulator. The rear gear should rotate approximately 3.75 turns. If the middle gear does not turn freely or at least 3.5 turns are not possible, replace the hydraulic modulator.

Refer to Brake Modulator/Master Cylinder Asm Replacement under On-Vehicle Service if replacement of the modulator is indicated above.

MANUAL CONTROL
This function can be used to manually control the ABS VI motors and solenoids.

MOTOR TEST (APPLY/RELEASE)
Each motor can be manually turned ON for up to five seconds, at a current of 10 amps in forward or 6 amps in reverse. After running the motors, the command and feedback currents will be stored in the snapshot buffer. This information can be reviewed to determine if the motors are operating properly.

The test below describes how the front motors will normally operate. The rear motor can be tested in a similar manner, except there will be only a slight pedal drop (bump) and rise during the test.
1. Turn the ignition switch to the OFF position.
2. Install a scan tool.
3. Turn the ignition switch to the RUN position.
4. Select SPECIAL FUNCTIONS, MANUAL CONTROL.
5. Pump brake pedal until firm to deplete vacuum from power booster.
6. Depress and hold brake pedal.

7. RELEASE the motor to be tested. The brake pedal should move smoothly toward the floor. As the pedal drops, the feedback current should momentarily drop to only a few amps (indicating motor movement) and then become equal to command current (6 amps). This indicates the motor is no longer moving since the piston has reached the bottom of the bore.
Rough or jumpy pedal movement indicates an intermittent electrical connection within the motor.

8. With the brake pedal still depressed and at the floor, `apply', the same motor. The brake pedal should now smoothly rise back to the top of its travel. The feedback current should momentarily drop to a few amps, then quickly increase to the command current (10 amps).
This indicates the motor is no longer moving since the piston has reached the top of the bore (home position).