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ABS AND BRAKE LIGHT ON HELP PLEASE

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chevhot Enthusiast

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Posted
Posted

after install of new tires they are 37/13.5 /18 i recaled the pcm speedo is right on the money but now i have the abs and brake lights on is there anything i can do to the abs ecu

please help if you can

thanks

rick

Haulin' 8.1 Enthusiast

Haulin' 8.1

Posted
Posted

Well in that case the problems not the tire size. ABS computers mainly compare speed differences between wheels and as long as the wheels all travel the same distance everything works regardless of the distance. Did you check the fluid level, really check it?

 

I just read your signature and see you've got some suspension mods. Check around each front wheel for damaged wireing and the single lead that plugs on top of the rear diff. If one of these wires got stretched out and broke or a tire rubbed it you'll loose that signal and loose ABS. Usually the ABS light would only come on. If both the ABS and BRAKE light are on you're either low on fluid or have a brake fluid hydraulics control problem in the ABS.

 

Did the lights come on right after the tire install or did it take a few days? And how long has it been on with you driving the truck? A lot of times if I run a vehicle on the lift with the drive wheels turning and the others still it will set an ABS code, but those usually clear once the vehicle reaches 45 MPH in normal condition.

 

Vernon

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Posted
  • Author
Posted

it happened as soon as i put the tires on i know the wires are ok

Haulin' 8.1 Enthusiast

Haulin' 8.1

Posted
Posted

At this point there's nothing I could tell you to go look at. Have a shop read the ABS codes for you and go from there. I can explain them if needed to double check the shop if necessary.

 

Vernon

Haulin' 8.1 Enthusiast

Haulin' 8.1

Posted
Posted

Rick at this point I don't think there's anything I can tell you to go look at and get it fixed. Find a place that can read the ABS codes for you and go from there. I can go over the codes with you if necessary.

 

Vernon

  • 3 weeks later...
pcrow Enthusiast

pcrow

Posted
Posted

Had a similar problem. Went from 3.42/235's to 4.10/265's. Within 1.5 miles the lights would come on every time. Hypertech used to re-program for tires & gears. Turns out that the ABS is programmed for wheel speeds also, using inputs from tranny output, as well as both front rotors. If speedo is cal'd for new gears/tires, it can be far enough away from the ABS calibration (certian combinations) to make the ABS unit think the front & rear wheels were constantly spinning at different speeds. This throws the lights and disables the ABS system. Hypertech said that their handheld (and I assume others) cannot program the ABS, so the only solution was to keep reducing what you enter for tire diameter until it goes away. I ended up with a speedo error of about 3%.

 

A lot of people never see this, as they are going with very big tires, and Hypertech only allows programming up to 34". Therefore, they are programming low anyway.

 

I have also been told that a PCM swap/tune can also correct the ABS programming...something the handhelds apparently cannot.

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