Hydraulic Control Assembly - Antilock Brakes: Testing and Inspection

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

Motor Test (Apply/ Release)
Each motor can be manually turned on for up to 5 seconds, at a current of 10 amps applied (forward) or 6 amps released (reverse). After running the motors, the command and feedback currents will be stored in a snapshot buffer. This information can be reviewed, when instructed to do so by the trouble tree, 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 ignition switch to "LOCK".
2. Install TECH-1 with ABS/Air Bag Cartridge.
3. Turn ignition switch to "ON".
4. Pump brake pedal until firm to deplete vacuum from power booster.
5. Depress and hold brake pedal.
6. Using the TECH-1, "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 (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.
7. 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).

Solenoid Test (On/Off)
Only use this test when no DTCs are stored and you suspect a leaky solenoid or check valve.
1. Turn ignition switch to "LOCK".
2. Install TECH-1 with ABS/Air Bag Cartridge.
3. Turn ignition switch to "ON".
4. Pump brake pedal and deplete vacuum from power booster.
5. Select manual control (FO).
6. Select left front or right front motor release.
7. Release the motor for the channel being tested. Review the motor command and feedback currents to be sure the motor released properly.
8. Select the solenoid for the same channel as that being tested.
9. With no brake pedal pressure applied, turn the solenoid on.
10. Depress the brake pedal. It should be very high and firm.

NOTE: If the pedal goes nearly to the floor, the solenoid is leaking or not closing and/or the check valve is leaking, proceed to Step 12).

11. With brake pressure still applied, turn the solenoid off. The brake pedal should move toward the floor. This verifies normal solenoid operation. END OF TEST.

NOTE: If the pedal does not, the solenoid is stuck on, proceed to Step 12).

12. Verify that the solenoid connectors are connected to the proper solenoids, (the right front solenoid is the one on the rear of the modulator, closest to the brake booster). If the wiring is incorrect, move the connectors to the proper solenoid and repeat this entire test starting with Step 1).
A. Physically switch the two solenoids.
B. Repeat the entire test starting at Step 1) for the channel in question.

^ If the test now works properly, test the other channel. If the test fails for this channel, replace the solenoid currently installed in this channel.
^ If the test fails for the same channel, the check valve is leaking. Replace hydraulic modulator.

WARNING: After performing Step 12) it is necessary to bleed the brake system.

HYDRAULIC CONTROL TEST (F2)
This test is used to verify base brake apply and ABS release, hold and apply function.
1. Turn ignition switch to "LOCK".
2. Raise the vehicle such that all wheels to be tested are off the ground.
3. Install TECH-1 with ABS/Air Bag Cartridge.
4. Turn ignition switch to "ON". Place transaxle into neutral.
5. Select a channel to test; left front, right front, or rear. When testing the rear brakes, both rear wheels should rotate and not rotate together at the various points in the test; this is true because both rear brake pressures are controlled together.
6. Firmly depress brake pedal. Pedal should remain high and firm.
7. Have an assistant attempt to rotate the wheel being tested. If the wheel does not rotate, base brake apply is working properly.
8. With the brake pedal still depressed, press the "^" key on the TECH-1 to start the test. The TECH-1 will display "Release" on the screen. Your assistant should be able to rotate the wheel being tested during the release portion of the test (approximately 2 seconds long). This verifies ABS pressure release. The brake pedal should remain high and firm. (If the brake pedal moves toward the floor, verify the solenoid electrical connectors are connected to the correct solenoids).
9. The TECH-1 will switch to the "Hold" mode and display the word "Hold" on the screen along with an 18 seconds decrement counter. With the brake pedal still depressed, have your assistant attempt to rotate the wheel. The wheel should rotate for the full 18 seconds of the test. This verifies ABS pressure hold.
10. When the hold portion of the test is complete, brake pressure will be applied and a slight bump may be felt in the pedal. This is normal. The assistant should not be able to rotate the wheel at the point. This verifies ABS apply.

MOTOR TEST (F4)
Once the motor pack has been separated from the ABS actuator (hydraulic modulator), this test will help to determine if the motor pack is operating properly. The TECH-1 will rotate 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.
The motor pack is not serviceable and must be replaced as an assembly.
^ If all three motors rotate, try to rotate each gear on the ABS actuator.

NO GEAR MOVEMENT
After the motor pack has been removed, rotate each gear by hand on the ABS actuator unit with large gears). The front gears (non-center gears) should be able to be rotated approximately five full turns lock to lock. If the gear does not turn freely or at least five turns are not possible, replace the ABS actuator.
Refer to "Hydraulic Assembly" if replacement of the ABS actuator is indicated above.

GEAR TENSION RELIEF (H)
When the displacement cylinder pistons are in the "home" position, each motor has prevailing torque. This torque results in "gear tension", or force on each gear that makes motor pack separation difficult. To avoid injury, or damage to the gears, the "Gear Tension Relief Function" briefly reverses each motor to eliminate the prevailing torque.
Always perform the "Gear Tension Relief Function" prior to removing ABS actuator assembly (the hydraulic modulator/motor pack assembly) from the vehicle.

RELAY TEST (F6)
This test allows the user to turn the relay on and off using the "^" and "V" keys on the TECH-1.
The battery voltage supplied to the EBCM through the relay contacts is displayed on the screen during the test. When the relay is commanded on, the voltage should be equal to the battery voltage. When the relay is off, the voltage should drop below 2 volts.

NOTE: Voltage will not drop to zero when the relay contacts are open due to capacitors in the EBCM. If voltage drops below 2 volts, the relay is operating properly.

VOLTAGE LOAD TEST (H)
This ABS can draw significant amounts of current when operating. This test turns on many of the system components to load-test the vehicle's electrical system.
If low voltage malfunctions or intermittent ABS operations are occurring, this test will allow you to monitor the ignition and switched battery inputs to the EBCM. If only one of these two inputs drops below 10 volts during testing, a high resistance may be present in that power feed circuit. If both inputs drop below 10 volts, the vehicle's electrical system needs to be diagnosed. In either case, the TECH-1 will display that the "Voltage Load Test" failed.

LAMP TEST (F8)
This test allows the user to control the indicator light associated with ABS. It can be used to check the lamp circuit including the ABS check relay (lamp driver relay). The amber "ABS" indicator light can be turned on, off, or flashed. The red "BRAKE" warning light and the blue "ABS ACTIVE" indicator light can be turned on and off.

SYSTEM ID (F9)
This feature is used to determine the ABS version.

MOTOR REHOME (H)
The motor rehome function is initiated by pressing the F5 key from the TECH-1 "Select Mode" menu.
The motor rehome function must ALWAYS be used prior to bleeding the brake system. This function will return all of the hydraulic modulator pistons to their upmost or "home" position. This allows all fluid paths within the modulator to be open so that the modulator can be properly bled.

CAUTION: The motor rehome function cannot be performed if any current DTCs are present. If current DTCs are present, the vehicle must be repaired and DTCs cleared before performing the motor rehome function.