ABS help please!
Thread Starter
Registered User
Joined: May 2004
Posts: 938
From: West Palm Beach Florida
ABS help please!
I took my 1997 Camaro Z28 to the dealer yesterday to get the ABS check out and they told me that I have to replace the "ABS motor pack".
And it will cost me about $500.00 bucks.
Now I can do it my self but there is a catch I have to do what is called a "Gear Tension Relief" on it before I can replace the motor pack.
So here is my question if the motor pack is not working how can they do a "Gear Tension Relief" on it?
I also talked to a friend on mine that's a mechanic for at least 8 years and he told me that all I would have to do is just bleed all the pressure out of it and I would be able to replace the Motor Pack.
So can any one confirm any of this can I just bleed all the pressure out and take the motor pack off.
Thanks for any help.
Chris G.
And it will cost me about $500.00 bucks.
Now I can do it my self but there is a catch I have to do what is called a "Gear Tension Relief" on it before I can replace the motor pack.
So here is my question if the motor pack is not working how can they do a "Gear Tension Relief" on it?
I also talked to a friend on mine that's a mechanic for at least 8 years and he told me that all I would have to do is just bleed all the pressure out of it and I would be able to replace the Motor Pack.
So can any one confirm any of this can I just bleed all the pressure out and take the motor pack off.
Thanks for any help.
Chris G.
Thread Starter
Registered User
Joined: May 2004
Posts: 938
From: West Palm Beach Florida
Re: ABS help please!
TTT
Well this is what I found out so far looking on the Internet.
Servicing Delco ABS VI
While radically different in design, Delco's ABS VI is one of the most technician-friendly antilock brake systems on the market.
GM's ABS VI system has been used for a kv number of years on many of their lighter vehicles. There's also a version that provides traction control. ABS VI is one of the more technician-friendly braking systems in use. There are many DTCs available, and the scan tool plays an important role in diagnosis and service. This article takes a look at some of the more useful diagnostic functions that are built into this system.
All antilock brake systems control wheel slip during braking by modulating hydraulic fluid pressure to the wheels. ABS VI uses a unique method of performing this task-motors that vary the displacement of fluid chambers.
The hydraulic modulator assembly mounts to the side of the master cylinder and is placed in line with the calipers and wheel cylinders. ABS VI is capable of both removing and applying braking force. It's a three-channel design in that it controls the front wheels separately and the rear wheels as a pair.
When the Electronic Brake Control Module (EBCM) senses wheel slippage from one of the wheel speed sensors, it isolates that hydraulic circuit from the master cylinder, then increases the displacement by lowering a piston in the displacement chamber. This effectively reduces the apply pressure to the brake on the slipping wheel. Once the affected wheel picks up speed that equals that of the others, the motor reapplies hydraulic pressure to the circuit under control and the system is ready for another go-round.
Diagnosis
GM recommends that diagnosis on ABS VI begin with a "Diagnostic System Check." Start with a preliminary inspection of the master cylinder fluid reservoir to make sure the brake fluid level is correct. While you're in the area, check for contamination, leaks and wiring damage.
Next, inspect the brake components of all four wheels to ensure that no drag exists and that the conventional braking system is operating properly. Also check for worn or damaged wheel bearings that may cause a wheel to wobble and affect brake operation.
Make sure the wheel speed sensors and sensor wiring are in good shape. This is a common source of illumination of the Brake warning lamp. The sensors should be solidly attached and the wiring should not show signs of rub-through or other damage.
Now connect your scan tool to see if any DTCs are displayed. If multiple codes are present, select DTC History to determine which malfunction occurred most recently. Diagnose and repair this malfunction first.
After recording the DTCs, clear them and see if any reappear. If a DTC does reappear, it's a "hard" fault and should be repaired first.
Be aware that a test drive may be required to reset a code. You can use the snapshot mode of your scanner to capture data when the DTC does set. If normal driving doesn't set a code, you may need to perform an ABS stop on a surface such as gravel to recreate the conditions. Be careful during the test drive!
Your scan tool has additional features that will help make diagnosing this system easier. For instance, you can monitor system data while manually controlling certain key components to perform the following specialized tests and procedures:
Motor Test (Apply/Release). Each motor on ABS VI can be switched on for up to 5 seconds. During the test, current is controlled at 10 amps in Forward and 6 amps in Reverse. After operating the motors, current information will be stored and can be reviewed to determine if the motors are operating properly. There'll be a slight pedal drop and rise during the test.
Here's how to perform it: With your scanner connected, select the motor you want to test. Next, pump the brake pedal to deplete vacuum from the power booster. Now depress and hold the pedal, then release the motor with the scan tool. The brake pedal should move smoothly toward the floor. Erratic pedal movement here may indicate an intermittent electrical connection within the motor.
With the brake pedal still depressed to the floor, now use your scanner to apply the same motor. The brake pedal should smoothly rise back to the top of its travel until the piston has reached the top of its bore (home). Repeat the test for the remaining motors.
Solenoid Test (On/Off). The solenoids can be tested by first releasing the motor for the circuit you want to test, then turning on the solenoid. When you stomp on the brake pedal, it should be very high and firm. If the pedal goes nearly to the floor, the solenoid may be leaking or not fully closing, and/or the check ball may be leaking. While holding pressure on the pedal, turn the solenoid off with your scanner. The brake pedal should drop immediately.
Hydraulic Control Test. This test is used to verify the brake system's ability to apply, as well as release, hold and reapply hydraulic pressure.
With all wheels off the ground, select the channel to be tested, then firmly depress the brake pedal. It should remain high and firm. At this point, have an assistant attempt to rotate the wheels) under test. If it doesn't rotate, that channel is working properly.
With the brake pedal still depressed, press the correct key on your scan tool to start the hydraulic test. The brake pedal should remain high and firm. With the pedal still depressed, have your assistant attempt to rotate the wheel(s). It should rotate with little or no resistance, indicating a proper release function. After an 18-second delay, brake pressure will be applied and a slight bump may be felt in the pedal. Now your assistant shouldn't be able to rotate the wheel(s).
Motor Test. Each motor can be tested once the motor pack is removed from the hydraulic modulator.
Gear Tension Relief Sequence. When the displacement pistons are in their normal braking (upper) position, each motor will be loaded to ensure that the pistons are held firmly at the top of their travel. This tension, however, can make motor pack separation difficult. To avoid injury or damage to the gears, the gear tension relief sequence briefly reverses each motor and eliminates any problem.
You should always perform the gear tension relief sequence prior to removing the hydraulic modulator or the motor pack from the vehicle. This includes the replacement of a master cylinder.
Relay Test. The voltage available to the EBCM while turning the Electronic Brake Control Relay on and off is monitored during this test.
When the relay is on, the voltage displayed on your scanner should be battery voltage. When the relay is turned off, the voltage should drop below 5 volts. Note that the voltage won't drop all the way to zero when the relay contacts are open due to a circuit in the EBCM.
Voltage Load Test. The ABS VI system uses a lot of current when operating, so it should be tested under load. This test turns on several components to loadtest the vehicle's electrical system. It's useful in diagnosing low-voltage malfunctions or intermittent EBCM operation. Using the scan tool, you can monitor both the ignition supply to the ABS and battery voltage during the test.
Rehome Function. The motor rehome function will return all of the hydraulic modulator pistons to their normal braking, or upper, position. This allows all fluid paths within the modulator to be open so the modulator can be properly bled. The motor rehome function must be used prior to bleeding the brake system or fluid will not pass through the modulator.
Note that the rehome function cannot be performed if any current DTCs are stored. If codes are present, repairs must be made and the codes cleared.
DTC Info
There's some useful information in the DTC History function of the scan tool that will provide clues as to how recently and how often a DTC set. This information is available for the first five codes, as well as the last code stored. Here's what the History function can give you:
*DTC number.
*Number of occurrences.
*Number of drive cycles since the first occurrence.
*Number of drive cycles since
the last occurrence.
The first five DTCs are stored in the order they occur. This order can then be used to determine if a previous malfunction is the root cause of a more recent one.
For example, a DTC that set only once over a large number of drive cycles will be difficult to find. On the other hand, if the code set on the last drive cycle, it's probably current. Another example is a DTC with an occurrence count of 15 out of 30 cycles, with a first occurrence of 30 and a last occurrence of 15. From this we can infer that a repair was made 15 cycles ago, but the codes were not erased, since the fault did not reoccur.
So if the "motor pack" is bad I can't do a "gear tension relief".
So what do I do instead so I can replace the motor pack?
I was in a slavage yard today and saw the ABS with the motor pack on it with the bottom broke off so I can see the gears on it and they are under tension so when I take the motor pack off these three gears are going to spin like crazy.
Help please.
Chris G.
Well this is what I found out so far looking on the Internet.
Servicing Delco ABS VI
While radically different in design, Delco's ABS VI is one of the most technician-friendly antilock brake systems on the market.
GM's ABS VI system has been used for a kv number of years on many of their lighter vehicles. There's also a version that provides traction control. ABS VI is one of the more technician-friendly braking systems in use. There are many DTCs available, and the scan tool plays an important role in diagnosis and service. This article takes a look at some of the more useful diagnostic functions that are built into this system.
All antilock brake systems control wheel slip during braking by modulating hydraulic fluid pressure to the wheels. ABS VI uses a unique method of performing this task-motors that vary the displacement of fluid chambers.
The hydraulic modulator assembly mounts to the side of the master cylinder and is placed in line with the calipers and wheel cylinders. ABS VI is capable of both removing and applying braking force. It's a three-channel design in that it controls the front wheels separately and the rear wheels as a pair.
When the Electronic Brake Control Module (EBCM) senses wheel slippage from one of the wheel speed sensors, it isolates that hydraulic circuit from the master cylinder, then increases the displacement by lowering a piston in the displacement chamber. This effectively reduces the apply pressure to the brake on the slipping wheel. Once the affected wheel picks up speed that equals that of the others, the motor reapplies hydraulic pressure to the circuit under control and the system is ready for another go-round.
Diagnosis
GM recommends that diagnosis on ABS VI begin with a "Diagnostic System Check." Start with a preliminary inspection of the master cylinder fluid reservoir to make sure the brake fluid level is correct. While you're in the area, check for contamination, leaks and wiring damage.
Next, inspect the brake components of all four wheels to ensure that no drag exists and that the conventional braking system is operating properly. Also check for worn or damaged wheel bearings that may cause a wheel to wobble and affect brake operation.
Make sure the wheel speed sensors and sensor wiring are in good shape. This is a common source of illumination of the Brake warning lamp. The sensors should be solidly attached and the wiring should not show signs of rub-through or other damage.
Now connect your scan tool to see if any DTCs are displayed. If multiple codes are present, select DTC History to determine which malfunction occurred most recently. Diagnose and repair this malfunction first.
After recording the DTCs, clear them and see if any reappear. If a DTC does reappear, it's a "hard" fault and should be repaired first.
Be aware that a test drive may be required to reset a code. You can use the snapshot mode of your scanner to capture data when the DTC does set. If normal driving doesn't set a code, you may need to perform an ABS stop on a surface such as gravel to recreate the conditions. Be careful during the test drive!
Your scan tool has additional features that will help make diagnosing this system easier. For instance, you can monitor system data while manually controlling certain key components to perform the following specialized tests and procedures:
Motor Test (Apply/Release). Each motor on ABS VI can be switched on for up to 5 seconds. During the test, current is controlled at 10 amps in Forward and 6 amps in Reverse. After operating the motors, current information will be stored and can be reviewed to determine if the motors are operating properly. There'll be a slight pedal drop and rise during the test.
Here's how to perform it: With your scanner connected, select the motor you want to test. Next, pump the brake pedal to deplete vacuum from the power booster. Now depress and hold the pedal, then release the motor with the scan tool. The brake pedal should move smoothly toward the floor. Erratic pedal movement here may indicate an intermittent electrical connection within the motor.
With the brake pedal still depressed to the floor, now use your scanner to apply the same motor. The brake pedal should smoothly rise back to the top of its travel until the piston has reached the top of its bore (home). Repeat the test for the remaining motors.
Solenoid Test (On/Off). The solenoids can be tested by first releasing the motor for the circuit you want to test, then turning on the solenoid. When you stomp on the brake pedal, it should be very high and firm. If the pedal goes nearly to the floor, the solenoid may be leaking or not fully closing, and/or the check ball may be leaking. While holding pressure on the pedal, turn the solenoid off with your scanner. The brake pedal should drop immediately.
Hydraulic Control Test. This test is used to verify the brake system's ability to apply, as well as release, hold and reapply hydraulic pressure.
With all wheels off the ground, select the channel to be tested, then firmly depress the brake pedal. It should remain high and firm. At this point, have an assistant attempt to rotate the wheels) under test. If it doesn't rotate, that channel is working properly.
With the brake pedal still depressed, press the correct key on your scan tool to start the hydraulic test. The brake pedal should remain high and firm. With the pedal still depressed, have your assistant attempt to rotate the wheel(s). It should rotate with little or no resistance, indicating a proper release function. After an 18-second delay, brake pressure will be applied and a slight bump may be felt in the pedal. Now your assistant shouldn't be able to rotate the wheel(s).
Motor Test. Each motor can be tested once the motor pack is removed from the hydraulic modulator.
Gear Tension Relief Sequence. When the displacement pistons are in their normal braking (upper) position, each motor will be loaded to ensure that the pistons are held firmly at the top of their travel. This tension, however, can make motor pack separation difficult. To avoid injury or damage to the gears, the gear tension relief sequence briefly reverses each motor and eliminates any problem.
You should always perform the gear tension relief sequence prior to removing the hydraulic modulator or the motor pack from the vehicle. This includes the replacement of a master cylinder.
Relay Test. The voltage available to the EBCM while turning the Electronic Brake Control Relay on and off is monitored during this test.
When the relay is on, the voltage displayed on your scanner should be battery voltage. When the relay is turned off, the voltage should drop below 5 volts. Note that the voltage won't drop all the way to zero when the relay contacts are open due to a circuit in the EBCM.
Voltage Load Test. The ABS VI system uses a lot of current when operating, so it should be tested under load. This test turns on several components to loadtest the vehicle's electrical system. It's useful in diagnosing low-voltage malfunctions or intermittent EBCM operation. Using the scan tool, you can monitor both the ignition supply to the ABS and battery voltage during the test.
Rehome Function. The motor rehome function will return all of the hydraulic modulator pistons to their normal braking, or upper, position. This allows all fluid paths within the modulator to be open so the modulator can be properly bled. The motor rehome function must be used prior to bleeding the brake system or fluid will not pass through the modulator.
Note that the rehome function cannot be performed if any current DTCs are stored. If codes are present, repairs must be made and the codes cleared.
DTC Info
There's some useful information in the DTC History function of the scan tool that will provide clues as to how recently and how often a DTC set. This information is available for the first five codes, as well as the last code stored. Here's what the History function can give you:
*DTC number.
*Number of occurrences.
*Number of drive cycles since the first occurrence.
*Number of drive cycles since
the last occurrence.
The first five DTCs are stored in the order they occur. This order can then be used to determine if a previous malfunction is the root cause of a more recent one.
For example, a DTC that set only once over a large number of drive cycles will be difficult to find. On the other hand, if the code set on the last drive cycle, it's probably current. Another example is a DTC with an occurrence count of 15 out of 30 cycles, with a first occurrence of 30 and a last occurrence of 15. From this we can infer that a repair was made 15 cycles ago, but the codes were not erased, since the fault did not reoccur.
So if the "motor pack" is bad I can't do a "gear tension relief".
So what do I do instead so I can replace the motor pack?
I was in a slavage yard today and saw the ABS with the motor pack on it with the bottom broke off so I can see the gears on it and they are under tension so when I take the motor pack off these three gears are going to spin like crazy.
Help please.
Chris G.
Registered User
Joined: Oct 2003
Posts: 2,140
From: DOVER DE
Re: ABS help please!
Nothing is going to break when you take it apart. The motor pack has three small gears that drive three large gears on the ABS module. The gears are under quite a bit of tension. I just changed a master cylinder on a Lumina and had to take this apart because the ABS was bolted to the master cylinder.
Before you remove the motor pack, mark the large gears with something where they meet the small gears. To avoid loosing all the tension, I put several zip ties on the gears to tie them together. This made the gears easier to retension when I reassembled them.
Do you have a new motor pack?? I've got one off a 97 Z28 you could almost have (just pay shipping).
Before you remove the motor pack, mark the large gears with something where they meet the small gears. To avoid loosing all the tension, I put several zip ties on the gears to tie them together. This made the gears easier to retension when I reassembled them.
Do you have a new motor pack?? I've got one off a 97 Z28 you could almost have (just pay shipping).
Thread Starter
Registered User
Joined: May 2004
Posts: 938
From: West Palm Beach Florida
Re: ABS help please!
Yea I got it on Tuesday big deal at the dealer because they sold me the one for the traction control last year and I just put it on last week.
And of course it did not fix my ABS problem so I took the car back and they told me it was again the ABS motor pack and I got the right one for $100.00 bucks. 
Because they messed up and told me to get the wrong price and it was like $400 bucks.
Thanks so much for replying back.
Can you be a little more specific about where you used the zip ties?
Should I just tie one gear to the other?
Let me know your a life saver.
Chris G.
And of course it did not fix my ABS problem so I took the car back and they told me it was again the ABS motor pack and I got the right one for $100.00 bucks.
Because they messed up and told me to get the wrong price and it was like $400 bucks.
Thanks so much for replying back.
Can you be a little more specific about where you used the zip ties?
Should I just tie one gear to the other?
Let me know your a life saver.
Chris G.
Thread
Thread Starter
Forum
Replies
Last Post