Motor Testing

MOTOR TESTING
Tools Required
Scan Tool
Each motor can be turned on manually for up to 5 seconds at a current of 10 amps forward or 6 amps backward. The test below describes how the front motors will operate. The rear motor can be tested in a similar manner, except there will be only a slight pedal drop and rise (bump) during the test.
1. Turn the ignition switch to LOCK.
2. Install the brake cartridge into the scan tool and connect it to the data link connector (DLC). Power the scan tool using the battery adapter.
3. Turn the ignition switch ON, with the engine stopped.
4. Pump the brake pedal several times to deplete the vacuum reserve.
5. Press and hold the brake pedal.
6. Using the scan tool, release one of the motors. The brake pedal should move smoothly toward the floor. As the pedal drops, the feedback current should momentarily drop to only a few amps (indicated motor movement) and then become equal to the command current (6 amps). This indicates the motor is no longer moving since the piston has bottomed out.
- Rough or "jumpy" pedal movement indicates an intermittent electrical connection within the motor.
7. With the brake pedal still pressed to the floor, apply the same motor. The brake pedal should now rise smoothly back to the top of its travel. The feedback current should drop momentarily to a few amps, then quickly increase to the command current (10 amps). This indicates that the motor is no longer moving since the piston has reached the top of its travel.
If the brake pedal does not move both up and down as indicated and there are no DTCs set, monitor the feedback current closely while performing the test again. If the feedback current is only a few amps, the motor is free-spinning. The motor pack must be separated from the hydraulic modulator to identify an expansion spring brake (ESB), a motor, a gear, or a ball screw problem.