So my ABS system has been an issue for some time in which I have been trying to determine what sensor is bad and have not found an issue with any of the hub assembly's. Ultimately ended up scanning the system with newer scan tool and determined that it was most likely the ABS control Module. I replaced the module and it did not fix the ABS light.

After trying to determine the route of the problem and troubleshooting since when the ABS light came on my brake peddle became very hard and did not sink, however it does not apply pressure to the caliper/pad and allow me to stop.

My questions are as follows:

1. Could the master cylinder be bad?
2. If it is the master cylinder would it cause the ABS light to come on?
3. How do I tell if it is the master cylinder?
4. Could it be the control pump assembly that all the brake lines go out of and the control module mounts to? If so I can I tell to confirm?

Any help would be greatly appreciated.

Thank you

Derrick

 

Have you thoroughly checked the wiring to the wheels?

 

Yes, checked both the front and the rear wiring. Not sure if that would have an affect on the brake pedal not allowing me to stop.

 

I somehow missed the hard brake pedal. I would look at the vacuum lines going to it first. Make sure everything looks kosher.

Another way to test it, is by loosening a bleeder screw on the caliper, and turn the truck over, and press the brake pedal. See how it feels. It should sink right to the floor extremely easier than when you have the truck off. If it acts like I said, the brake master cylinder is likely good.

If it doesn't than it's likely either the master cylinder or the control module restricting the fluid.

Also, make sure your steel hoses are not kinked, and check your brake hoses. I've seen where brake hoses collapse and do very funky things.

 

Thank you. I will try both and let you know.

 

no sh*t SAME issue with MINE TODAY!!! almost exact same....ABS light has been intermittent for about a month now....all new brakes about 2 months ago ....normally working fine...ABS light comes on sometimes...brakes still work perfectly fine till TODAY.... ABS light comes on...all is well then as i need to get more brake, I push a little harder and Harder and HARDER and nothing is really changing. I am still not stopping relative to pedal effort. It is like you sprayed the rotors with WD40. The drive home today should be interesting...
Just ordered a new scan tool as my 14 yr old model does not do ABS and half the local stores will not let ME plug in their scanner and THEY have no clue what they are looking AT..

 

I have checked the brake power booster and changed the check valve on the booster thinking maybe it was that because it allowed some air by one way if you did not push too much air in one shot. I have not been able to check a caliper yet but did pull off the one line on master cylinder and was still able to get fluid to shoot out at the MC. Once I check caliper I will know if if the ABS control module pump/block is bad. I am hoping not because everything I have read states that you have to bleed that block with a special scan tool to activate the ABS system.

Good thing is this is not my daily driver. The only way I can it to stop is to put it in neutral and push real hard!

Let me know if you find anything else out.

 

My scanner arrives tomorrow....so I will start with the code that is activating ABS....then work from there. It is intermittent so.....going to suck i'm sure

 

Ok scanner is loaded. ..with stuff,
C1230, c1233, c1234 ...AND ....DUN DUN DUN
C1185....
So I need a control module. ...

Unless.....

Anybody.... know if codes are time stamped? ...what happened first?....
Loss of power.... THEN lack of input OR..... lack of input THEN loss of power (ie... short)
?

 

update!!....while driving i had scanner plugged in.... ....ABS lights up....1 code C1185....(no power) reset.... If I am able to reset a NO POWER then it must be control module BUT. I will obviously check the power supply to the HCU first ...just to rule that out.
however..
I still have NOT experienced ANY mechanical brake issue like the other morning......YET

 

Code 1185 is power relay...circuit...failure.
Code 1230 rear center sensor...circuit...failure.
Code 1233 is Left front signal missing.
Code 1234 is Right front signal missing.
.
Suggest a harness or a plugup issue for all these codes and the fault descriptions.
.
They are ABS function issues and do not/should not affect ''normal braking function.
As a brake system design, you would never want failure in an "assisting system" to affect the base brake system to a failure point of stopping the vehicle.

Make sense?
Good luck.

 

I have had multiple ABS lights as i drive....I keep my scanner pluged in.....each time has only been c1185 ONLY. did the pinpoint test at plug (volt test at pin 46 and 9) shows 11.8 volts....control module is bad.
going to MyAirbags to have them rebuild it....2 -3 day turnaround $100 ...

I have NOT had another base brake malfunction as of yet.....but fixing what i KNOW is bad first.....then see whats up. Bad part is I can NOT recall if the ABS light was ON during said issue or not.

 

Fbird

Have you checked grounds?

 

MY module rebuilt -> returned....all is well.
Best idea i come up with on the BRAKE malfunction is the ABS module not performing correctly activated a pressure DUMP without activating the PUMP...
have had no further issues. And YES you can drive these trucks WITHOUT the ABS module on the vehicle.

 

Fbird

Where did you have the module rebuilt?