Spongy brakes and Brake and ABS lights on

[Tbird9140]

( 2000 Ram 1 tn 4wd diesel auto, 340000 miles) Now that I got my fuel pressure issue solved, my brakes have decided to act up. They have been "spongy" and not strong stoppers for about 200 miles. I was going to wait till I got home to address the problem. Now however the Brake and ABS dash lights have come on permanently when driving. I also do not hear the semi loud "boom" I always heard in the past when turning the key on. I am aware of the sensor on the rear differential, but is this the kind of symptom that a failed sensor would cause?  Also is there not a 6 pin brake switch somewhere that occasionally fails. Any help or thoughts would be appreciated. Booster, master cylinder, wheel cylinders, etc. ????

[Mopar1973Man]

First off... Does the speedometer work properly? If the speedometer works correctly then the rear sensor is fine but the front to are suspect. 

 

I've seen bad tone wheels in the unit bearings cause a ABS/BRAKE light. But other than that its one of the 3 sensors. Best to replace both fronts the same time. Typically if you replace one sensor the other old sensor will trip because it will not match speeds with the new one. Once you fix the ABS problem all you gotta do is turn the key on, start and move about 100 yards with a bit of speed and the light will reset on its own. 

 

Might check for error  codes it might give more clues make sure to use a OBDII coder reader and not the key trick.

 

 

[Tbird9140]

Thanks for the possible solutions. After driving 50 miles the ABS and Brake lights turned off. Further, when I started the truck after a lunch stop l again heard the under the hood "boom" which had been missing all the time the ABS and Brake lights were on. (I am not sure if they are related), maybe you can educate me on the boom. In any case unless the brakes get worse, they are not great at stopping, I will probably try to limp home where I have more resources. Thanks again.

[Mopar1973Man]

You might have to get a ABS coder reader and see what the codes are being its a very random issue. Mine in the past was a bad tone ring in the right hand bearing in the front after replacing the wheel bearing both sides the code reset. Basically in a nutshell all 3 speed sensor (both front and rear axle) have to match to make the lights go off. Typically though the fronts are the source of the cause because if the rear was a problem the speedometer would act goofy. Meaning... The speedometer might sit at zero for extended period and then pop up later after movement started. Again this would be a bad rear sensor if so. ABS communication is not common so its special tool to read the ABS code. Even my Innova code reader has the function but not compatible with our year of Dodge. 

 

I heard that boom on one other truck which is some sort of after market device. This is not something that is normally heard. 

[Tbird9140]

My speedometer appears to work fine. Regarding "boom" on startup, I am not aware of any under the hood after market additions on the truck. I certainly have not added any. Further,  the boom has been there since I bought the truck. The only times I have not heard it (I recall)  is when the ABS and Brake lights have come on.  I plan to limp home and run the OBDII checks and sensor replacements you have suggested. Thanks.

[Mopar1973Man]

Yeah the boom noise it not typical. I'm now trying to figure out in my mind what it could be. I've only seen one other truck that did this. 

[Tbird9140]

If you ever figure out the "boom", please let me know. After a 150 miles of no dash warning lights, the ABS and Brake lights have come back on. When I start up truck, I get a ,"check brakes" notification for about two seconds, then it turns off. No "Check Engine" light while driving. I appreciate the help.

[Mopar1973Man]

Crazy idea try unplugging the ABS Module. See if the boom is gone. 

[IBMobile]

I was thinking the same thing.  The ABS module performs a self test on start up.

 

 

[Tbird9140]

I finally got home with the intermittent Brake and ABS dash lights keeping me awake, off and on, for the last 1000 miles.  Haven't noticed the "Boom" now for some time on startup.  Time now to address the brake warning light issues.  It was recommended that I replace the front wheel ABS (Speed?) sensors to see if this fixes the problem.  As the sensors are about $10 each on Ebay, I guess this means that I should simply replace BOTH sensors to try and fix the warning light issue this way???   If this doesn't permanently fix the problem, any suggestions on what I should do next??

I also plan to go to my local Oreilly's and have them do an OBDII code read for me.  Maybe this will give me some additional info on the brake light issue.

 

 

[Mopar1973Man]

Remember like in my case the sensors were good but the tone wheel broke the spot welds and cause the sensor error. So yes sensor first if no change then do unit bearings next. Or skip that just do wheel bearings up front with sensors. I've seen one member with wore bearings and tone wheel was no longer lining up with the sensor. Be careful those cheap sensors might not be good quality either. Get what you pay for, cheap sensors cheap performance.

Edited October 19, 2021 by Mopar1973Man