ABS IS ACTING WEIRD

pirotec354

pirotec354

Member
Aug 28, 2008
127
0
16
Grand Rapids, Michigan
#1
Ok so I have a 94 cobra and lately when I go and start the car the ABS light flickers and when I drive down the road and brake, I can feel the brake pedal kicking back at me. And this is on completely dry pavement. And it kinda feels like its pulsing the brakes a little when im actually driving down the road cuz I can feel my car like almost studdering? I really dont know how to explain how it feels. But any help would be great guys cuz this is really starting to bother me. Thanks!
 
#2
Youll have to get the codes pulled and I can give you a pinpoint test to follow. Though some of the codes are pretty obvious. I.E. codes for specific wheel sensors "usually" mean the sensor has gone bad. Most you can do without pulling codes is check out the wheel speeds sensors for any obvious signs of problems, like broken wires or cracked sensors, etc. Check the ABS electrical connector Ive seen them short out and melt to a smokey pile of ruin, causing severe problems and more shorts and blown fuses.
 
#3
Zero_chance said:
Youll have to get the codes pulled and I can give you a pinpoint test to follow. Though some of the codes are pretty obvious. I.E. codes for specific wheel sensors "usually" mean the sensor has gone bad. Most you can do without pulling codes is check out the wheel speeds sensors for any obvious signs of problems, like broken wires or cracked sensors, etc. Check the ABS electrical connector Ive seen them short out and melt to a smokey pile of ruin, causing severe problems and more shorts and blown fuses.
Click to expand...

Ok i can try and pull some codes but my check engine light isnt on its just the ABS light that is on all the time. Will i still be able to pull saved codes without the check engine light being on? Seems like they would all be cleared if it wasnt. Do you know where the ABS electrical connector is located at? I have a haynes manual but its not real clear on the ABS system.
 
#4
The ABS connector is under the hood usually clipped into a red housing with the words ABS self test connector. Pretty sure its mounted to the front of the driver side shock tower. Been a while since I messed with it.
 
#8
I had the same issue with my ABS a couple years ago....freaked me out as i was going down a hill.
But i traced mine to a short in the wiring, repaired it, replaced fuses and it was still sketchy. I removed mine as i dont plan to be driving in bad conditions and not more than 2k miles a year. preferences.....
 
#9
OK i pulled the code tonight and i got a code 63- voltage supply interruption (detects ignition voltage but not voltage for ABS controller). Im going to check the fuse in the engine bay and one under the dash tomorrow b/c its too dark now. But does anybody have a pinpoint test for this. It would be really helpful. Thanks
 
#10
Funny, I think thats the same code i have but my bulb burned out... out of sight out of mind. Ill grab that pinpoint test for you. Maybe it will even inspire me to fix mine..... wouldnt count on it though....

PINPOINT TEST D: HYDRAULIC PUMP MOTOR AND RELAY

D1 CHECK 60A ABS FUSE
Check the 60A ABS fuse located in the LH engine compartment power distribution panel.
Is the fuse OK?
Yes
GO to D4 .

No
GO to D2 .


D2 CHECK HYDRAULIC MOTOR SYSTEM
Ignition switch OFF.
Replace the 60A ABS fuse.
Inspect the fuse.
Does the fuse fail again?
Yes
GO to D3 .

No
GO to D4 .


D3 CHECK FOR SHORT TO GROUND IN HYDRAULIC MOTOR POWER CIRCUIT
Ignition switch OFF.
Remove the 60A ABS fuse.
Remove cover from hydraulic control unit.
Disconnect the 16-pin connector located at the hydraulic control unit.
NOTE: Circuit 601 changes color from LB/PK to R as it passes through the harness connector.

Measure the resistance of Circuit 601 (R) between the 60A ABS fuse terminal and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to D4 .

No
SERVICE Circuit 601 (R) between the engine compartment fuse panel and the hydraulic control unit.


D4 CHECK POWER SUPPLY TO HYDRAULIC CONTROL UNIT
Ignition switch OFF.
Disconnect the hydraulic control unit connector.
NOTE: Circuit 601 changes color from LB/PK to R as it passes through the harness connector.

Ignition switch ON.
Measure the voltage on Circuit 601 (R) at the hydraulic actuator assembly connector.
Is the voltage greater than 10 volts?
Yes
GO to D5 .

No
SERVICE Circuit 601 (R) between the engine compartment fuse panel and the hydraulic control unit.


D5 CHECK HYDRAULIC ACTUATOR ASSEMBLY GROUND
Ignition switch OFF.
Measure the resistance of the BK wire between the screw terminal on the right side of the hydraulic control assembly and ground.
Is the resistance less than 5 ohms?
Yes
REPLACE ABS unit.

No
SERVICE the BK wire.
 
#11
Alright cool thanks Zero_Chance for that. Well after doing that, i have found that the control unit is bad so i just disconnected the power supply to it for now. Having said that, the kickback in the pedal is gone but now i have a slight vibration at about thirty mph that wasnt there before. I put a center cap in my front passanger wheel b/c there was one missing, would doing that throw the wheel out of balance? I wouldnt think that it would.
 
#12
Theoretically, nothing that you did (at least, nothing that youve stated here) should cause any type of vibration at all. A center cap would definitely not cause a wheel to go out of balance, Id be checking other areas. Wheels are balanced without center caps so wed all be having issues with vibrations if that was the case. Hmmm. Did you take any wheels off? All lug nuts tight? Did any of the wheel weights get moved or fall off? Where do you feel the vibration? Steering wheel? Seat? Whole vehicle? Any noise? Get better or worst with higher speed? Answering these questions will help me and anyone else who chimes in try to figure this out with you.
 
#13
Yea i took all my wheels of to check my wheel speed sensors and ive double checked the lugs and made sure that they were tight. I can feel the vibration in my clutch and the steering wheel just a little bit. I can feel the vibration the best at 30 mph but if i go any faster it gets better and goes away. I checked all the weights on the wheels to and they all looked good but maybe one could have fell of or something and yes there is a slight noise too. Like a wah wah wah or something like that.
 
#14
Nine times out of ten any vibration felt in the steering wheel is coming from the front wheels. With a balance issue though, its usually starts at lower speeds and gets progressively worst. Interesting mystery. Does the noise fade off with the vibration or is the noise constant? I have a feeling this is gonna be one of those ones that I wish you lived in MA or CT so I could go for a ride with you... So am I correctly assuming that this WASNT happening before the ABS thing or is it possible it was there and you just didnt notice it? Have you been driving the car consistently or is just out of winter storage? Sorry so many questions.
 
#15
Zero_chance said:
Nine times out of ten any vibration felt in the steering wheel is coming from the front wheels. With a balance issue though, its usually starts at lower speeds and gets progressively worst. Interesting mystery. Does the noise fade off with the vibration or is the noise constant? I have a feeling this is gonna be one of those ones that I wish you lived in MA or CT so I could go for a ride with you... So am I correctly assuming that this WASNT happening before the ABS thing or is it possible it was there and you just didnt notice it? Have you been driving the car consistently or is just out of winter storage? Sorry so many questions.
Click to expand...
Oh no its fine. But yea i just got the car out of winter storage about a month ago but its been driving fine ever since. I did a complete tune up right when i got it out, changed all the fluids and everything. Then it started doing the ABS thing and know all of a sudden its doing this. I cant really tell if the vibration and the noise go away the faster i go bc my car is so loud. But i can definetely tell you that it doesnt do it as bad the faster i go. And the noise is consistant with the vibration.
 
#16
Have u checked the condition of the exciter rings all the way around?
Also is it possible to have hit something in the general time frame of the abs problem happening the HCU (hydraulic control unit) is in the vicinity of alot of your front end components. Long shot but possible helpful ideas
 
#18
If your talking about the rings that the wheel sensors read off of then yes, i checked them on every wheel when i checked the sensors, and they seemed to be ok. And i dont think i hit anything when i was checking the hcu, i was pretty careful there. But no i havent checked the e-brake or the cable, could it be possible that something is pulling on it just a tad and keeping it just barely engaged? Or maybe the cable could just be worn?
 
#19
I was thinking along those lines, it kind of reminds me of a car that came into the dealership with similar problems. The driver side ebrake was still engaged even though the pedal was released. Something worth looking at if you get it on jackstands again.
 
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