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Packard 10-16-2018 07:39 AM

abs lessons to learn
Update on ABS: I replaced the ABS motor pack this weekend with one that I got at a local junkyard & felt I might as well fill & flush the entire brake system with new brake fluid. I first bled the system the standard "Pump Brake Pedal" method until fresh brake fluid exited all the bleeder valves. The second bleeding method involved cycling the electric motors & solenoid valves with the "Special Scanner" to properly flush the old fluid from the hidden passages. Well, I do not have one so I had to IMPROVISE. The procedure states to first "Run" the motors down to relieve tension which simplifies the safe removal of the motor pack . Once the motor pack is replaced, you then run the motors up to reapply tension. I accomplished this by snipping a motor pack wiring harness from the junkyard & installing it onto the new motor pack. I then took 12 VDC from my battery & applied it directly to each set of motor leads to run the motors in one direction. I then reversed the leads which runs the motor in the opposite direction (up or down, etc). I repeated this on the 2 solenoid valves at the top. The entire brake system took about 1 1/2 hours to bleed until all brake fluid exiting was clean. Total cost was $30 for 2 bottles of brake fluid, the motor pack, & my labor. The ABS & Brake lights no longer stay on. For about $100 I was able to resolve my transmission problems & ABS. Thanks to all who have helped.

I worked on that ABS system when it was being developed. The motors and ballscrews don't take to kindly to having 12 volts applied directly to them. They are designed to have a Pulse Width Modulated (PWM) signal to lower the average operating current when they are being run up and down. When you apply 12 volts directly to the motors, you will slam the ballscrews at the top and bottom of the bore risking breakage. The dealers use a scan tool to send commands to the ABS ECU for the bleed routine. You will be fortunate if you didn't break anything in the process.

If you are just replacing the motorpack, then no bleeding was necessary.

fdryer 10-16-2018 02:06 PM

Re: abs lessons to learn
Did you verify abs operation on a wet, gravel, or dirt road?

Packard 10-17-2018 05:01 AM

Re: abs lessons to learn

fdryer 10-17-2018 03:40 PM

Re: abs lessons to learn
Drawings are great but doesn't answer the question whether or not abs works. Virtually all abs brakes give back a foot massage to the brake pedal from the high speed cycling of brake valves opening and closing as increased hydraulic pressure is applied and released to the locked wheel(s) to prevent wheels from locking up. If the abs light turns on and stays on after turning on ignition, the abs self test failed and disables abs operation. Under normal circumstances, the abs light turns on at ignition on time to indicate it's performing its own power-up self tests. If initial self tests pass (wheel speed sensors detected, wiring to wheel speed sensors intact, abs module electronics pass self tests) the abs light turns off. Once the car moves above approximately 5 mph, another part of abs operation tests the motor unit and solenoid valves - most drivers hear a zinging sound for a second. This sound only occurs at initial drive off every time the engine is started and car driven above 5 mph. If this test goes well, the abs light remains off with abs on standby mode ready to activate during emergency braking.

Packard 10-17-2018 09:52 PM

Re: abs lessons to learn
So first test if on ignition on what things are tested working when light goes off without vehicle movement ? What things can I eliminate as good parts?

Packard 10-17-2018 10:05 PM

Re: abs lessons to learn
so then I can surely say my sensors are fine then . If from what your telling me and others here say the first test is the 4 wheel sensors. So also my abs module is ok then right?

I have tested the 5mph and light is on at 5mph only.

So what can i do to fix the 5mph issue? Replace whole unit from donor car ?
Bleed my existing unit? Do any of these fixes work??

fdryer 10-18-2018 01:57 PM

Re: abs lessons to learn
[QUOTE] The normal sequence for ABS system self checks occurs from ignition ON time when the ABS light cycled on and off to inform the driver that initial ABS self tests (electronics) have passed otherwise the ABS light will remain ON. When driving off, ABS initializes itself by monitoring wheel speed sensors and activating its motor to continue self tests and if all goes well all you hear is a momentary 'zinging' sound. Zinging occurs around 5-10 mph. ABS always starts from all its valves closed whether or not failure occurred (ABS light staying ON ) to stay invisible to the main braking system so it can never interfere with braking if it fails. [/QUOTE]
This info came from the '02 SC2 service manual. I'm quoting from another thread you replied to. I presume its backward compatible with previous abs versions. If we can presume this applies to older S-series abs brakes then the initial abs light turning on and off at ignition on time suggests the abs module is fine. When driving off and the abs light turns on, this suggests a faulty wheel speed sensor, reluctor or wiring to each wheel speed sensor.

Packard 10-21-2018 12:41 AM

Re: abs lessons to learn
DELCO (DELPHI) ABS-VI (4-wheel, Nonintegral)

1991 & up Buick Skylark GS

1991 & up Oldsmobile Cutlass Calais International

1991 to 2000 Pontiac Grand Am SE

1991 & up Saturn

1992 to 1999 Buick Regal

1992 & up Chevrolet APV, Beretta, Cavalier, Corsica, Lumina

1992 to 1997 Geo Prizm

1992 to 1999 Oldsmobile Achieva, Cutlass, Silhouette

1992 to 1998 Pontiac Grand Prix

1992 & up Pontiac LeMans, Sunbird & Transport

1993 to 1998 Chevrolet Camaro

1993 to 1998 Pontiac Firebird

1994 & up Oldsmobile Delta 88, 98

Packard 10-21-2018 03:28 AM

Re: abs lessons to learn

Packard 10-21-2018 03:50 AM

Re: abs lessons to learn

Packard 10-21-2018 04:42 AM

Re: abs lessons to learn

Packard 10-21-2018 04:43 AM

Re: abs lessons to learn

Packard 10-21-2018 04:44 AM

Re: abs lessons to learn

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