ABS not working, but no warning lights??
03-24-2016, 12:10 PM
#1
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ABS not working, but no warning lights??
I was at my first PCA DE (Intro Driving School) last summer, and during the skid pad exercises it was clear that:
a) my brake modulation is exceptional
because
b) my ABS wasn't functioning
I don't have any brake-related warning lights lit up on my instrument cluster.
Any thoughts on what might be wrong or how to diagnose?
TIA!
a) my brake modulation is exceptional
because b) my ABS wasn't functioning
I don't have any brake-related warning lights lit up on my instrument cluster.
Any thoughts on what might be wrong or how to diagnose?
TIA!
03-24-2016, 01:35 PM
#3
Drifting
I was at my first PCA DE (Intro Driving School) last summer, and during the skid pad exercises it was clear that:
a) my brake modulation is exceptional because
b) my ABS wasn't functioning
I don't have any brake-related warning lights lit up on my instrument cluster.
Any thoughts on what might be wrong or how to diagnose?
TIA!
a) my brake modulation is exceptional
because b) my ABS wasn't functioning
I don't have any brake-related warning lights lit up on my instrument cluster.
Any thoughts on what might be wrong or how to diagnose?
TIA!
Did you hit the brakes and locked up the wheels? Your brake modulation is exceptional because ABS works! If ABS is not working you should be locking wheels meaning your modulation is not great.
03-24-2016, 02:02 PM
#4
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you can feel abs working.
i have this issue on my 964. no lights, abs pump runs, no abs.
Issue is the abs unit
the way this works is a series of valves - computer detects wheel lockup, and the pump varies the brake pressure by pulsing the wheels. The pump will 'lock' the wheel but it will not 'unlock' the wheel.
fix is pump replacement
go out when it is wet and slam on your brakes in a safe area and a low speed. don't do in dry unless you like flat spots
i have this issue on my 964. no lights, abs pump runs, no abs.
Issue is the abs unit
the way this works is a series of valves - computer detects wheel lockup, and the pump varies the brake pressure by pulsing the wheels. The pump will 'lock' the wheel but it will not 'unlock' the wheel.
fix is pump replacement
go out when it is wet and slam on your brakes in a safe area and a low speed. don't do in dry unless you like flat spots
03-24-2016, 02:49 PM
#5
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Sorry – my mistake. Not SKID PAD, it was the threshold braking exercise (which involved some skidding on my part).
I know the ABS wasn't working because I'm able to lock up the brakes and skid for as long as I choose to.
Sorry for the confusion!
I know the ABS wasn't working because I'm able to lock up the brakes and skid for as long as I choose to.
Sorry for the confusion!
03-24-2016, 02:53 PM
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I discussed it with my instructors too since they were surprised to see the wheels lock during the exercise. In fact, the whole point was to find the point at which the ABS would kick in.
03-24-2016, 02:57 PM
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you can feel abs working.
i have this issue on my 964. no lights, abs pump runs, no abs.
Issue is the abs unit
the way this works is a series of valves - computer detects wheel lockup, and the pump varies the brake pressure by pulsing the wheels. The pump will 'lock' the wheel but it will not 'unlock' the wheel.
fix is pump replacement
go out when it is wet and slam on your brakes in a safe area and a low speed. don't do in dry unless you like flat spots
i have this issue on my 964. no lights, abs pump runs, no abs.
Issue is the abs unit
the way this works is a series of valves - computer detects wheel lockup, and the pump varies the brake pressure by pulsing the wheels. The pump will 'lock' the wheel but it will not 'unlock' the wheel.
fix is pump replacement
go out when it is wet and slam on your brakes in a safe area and a low speed. don't do in dry unless you like flat spots
It was raining during my DE, so there was a lot of opportunity to confirm that my wheels were locking during the braking exercise.
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03-24-2016, 02:58 PM
#8
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I should add. This is pretty common. The pumps are getting old, they don't get exercised very often, and the pistons and valves that control the fluid flow get gummed up.
03-24-2016, 07:04 PM
#9
Three Wheelin'
Just an idea, but does your car have ABD? If so, perhaps having some one bleed the system with the help of a Porsche tester to activate the ABS pump may dislodge some gunk?
05-14-2016, 03:05 PM
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05-14-2016, 04:17 PM
#12
See here...https://rennlist.com/forums/993-foru...code-m224.html
If memory serves, bruce7 posted a DIY to pump the ABD, without the use of a hammer, pst2, or piwis diag tester.
If memory serves, bruce7 posted a DIY to pump the ABD, without the use of a hammer, pst2, or piwis diag tester.
05-14-2016, 04:53 PM
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Thanks for all the replies.
So, the approach being suggested is to find a method (via OBD2 tool or otherwise) to trigger the ABD system (if present) to try to see if we can get the system to respond and pulse? If no response, the pump is probably toast?
So, the approach being suggested is to find a method (via OBD2 tool or otherwise) to trigger the ABD system (if present) to try to see if we can get the system to respond and pulse? If no response, the pump is probably toast?
05-14-2016, 08:48 PM
#15
I found this in my subscribed threads...HTH
Jyster sent me this and I used it with success to actuate the valves while my son pumped the pedal slowly and I had only about 10 psi applied to the pressure bleeder. I would crack the bleeder, go to the boot and actuate the valves with an alligator clip. You must understand which valves do what so that when you open the bleeder you are actuating the appropriate valves. I could hear bubbles rushing out. I actually had my abs unit out on my bench to clean it. Actuating the valves at that time allowed chunks of trapped spooge to come out.
My car is ABS only, no ABD. That is, three channel not 4. So, I suggest you determine if this particular pin configuration will work.
Once the unit is out and cleaned, it's full of air. I went through about 8 liters of dot3 for flushing and then about 2liters of cheap dot4. I ran cheap dot4 for about two weeks, flushed again with ATE 200. No more spooge...
If your ABS light was on already, it will still be on. With All that done, you still have to have a piwis or that other device in order to run diagnostics. The system is disabled by design when the fault occurred. I believe, from reading (a lot) that it will not retest and enable ABS autatically.
So... ABS on my cat is still out, but the pedal feel is greatly improved. The local P shop said it would be about 2 hours labor to check the system and tun diag.
You cannot flush the system or even bleed it affectively with the wheels on. Each caliper has two bleed screws. The inner one is not accessible with wheels on.
Here is the message from jyster
Quote:
Originally Posted by jstyer
Jeremy, Power is applied to pin 15 of the ABS unit. You will ground out the following pins back to the battery, depending on which valve you want to open. The valves are as follows: Pin 7: Inlet Valve Front Left Pin 6: Exhaust Valve Front Left Pin 8: Inlet Valve Front Right Pin 5: Exhaust Valve Front Right Pin 10: Inlet Valve Rear Pin 11: Exhaust Valve Rear My process in cleaning my ABS unit was to power up the valves on each circuit and blast high pressure air and brake cleaner through the system while the valves were open. Before you remove the ABS to try and give it a clean, I'd try to just supply power to the valves and see if they open. There's an audible click when they cycle open. It's quiet, but you can definitely hear it. Hope this helps man. Brake problems can be a real bitch on these cars. When I first got my car, I had it apart for weeks trying to sort out a totally failed brake system. It was definitely frustrating. In the future after you get it sorted, just remember to flush fluid 12-18 months. It seems like overkill, but it really helps the longevity and performance of these early ABS based braking systems. Keep me updated, as I'd like to see if you get the ABS unit back up and running. Regards, Justin
My car is ABS only, no ABD. That is, three channel not 4. So, I suggest you determine if this particular pin configuration will work.
Once the unit is out and cleaned, it's full of air. I went through about 8 liters of dot3 for flushing and then about 2liters of cheap dot4. I ran cheap dot4 for about two weeks, flushed again with ATE 200. No more spooge...
If your ABS light was on already, it will still be on. With All that done, you still have to have a piwis or that other device in order to run diagnostics. The system is disabled by design when the fault occurred. I believe, from reading (a lot) that it will not retest and enable ABS autatically.
So... ABS on my cat is still out, but the pedal feel is greatly improved. The local P shop said it would be about 2 hours labor to check the system and tun diag.
You cannot flush the system or even bleed it affectively with the wheels on. Each caliper has two bleed screws. The inner one is not accessible with wheels on.
Here is the message from jyster
Quote:
Originally Posted by jstyer
Jeremy, Power is applied to pin 15 of the ABS unit. You will ground out the following pins back to the battery, depending on which valve you want to open. The valves are as follows: Pin 7: Inlet Valve Front Left Pin 6: Exhaust Valve Front Left Pin 8: Inlet Valve Front Right Pin 5: Exhaust Valve Front Right Pin 10: Inlet Valve Rear Pin 11: Exhaust Valve Rear My process in cleaning my ABS unit was to power up the valves on each circuit and blast high pressure air and brake cleaner through the system while the valves were open. Before you remove the ABS to try and give it a clean, I'd try to just supply power to the valves and see if they open. There's an audible click when they cycle open. It's quiet, but you can definitely hear it. Hope this helps man. Brake problems can be a real bitch on these cars. When I first got my car, I had it apart for weeks trying to sort out a totally failed brake system. It was definitely frustrating. In the future after you get it sorted, just remember to flush fluid 12-18 months. It seems like overkill, but it really helps the longevity and performance of these early ABS based braking systems. Keep me updated, as I'd like to see if you get the ABS unit back up and running. Regards, Justin