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When starting my truck, it goes through the typical light up of lights on the dash and all go out. When I start driving and brake the RABS and Parking Brake Light come on and stay on. I pulled a RABS light flash code of 4, which means "Open of Shorted Valve Switch or Harness". Can someone help me understand what I need to do from here? What is most likely the issue with this code? Is there further diagnostics that I can do to help trouble shoot and fix this. If I can't fix it by next week I will have to take it in to get fixed and I would rather fix it myself if possible and save that money for my kids Christmas.
Since you are getting RABS codes I assume the Red Brake lamp is not lit when you initiate the code flashout. By design the RABS system will not flash out codes with an active Red brake lamp. Based on your statement "When I start driving and brake the RABS and Parking Brake Light come on and stay on." I would suggest you verify the brake fluid level. There is a float in the reservoir that will close the circuit switch for the Red brake lamp when the fluid is too low. With low fluid, but not enough to trigger the Red brake lamp with the truck sitting, the fluid level could drop enough under operation for the float to drop which in turn triggers the Red brake lamp. This will also trigger the Yellow ABS lamp with a Code 12.
Why did you get Code 4 you ask....the RABS-II system does store codes, but it only shows the last one triggered. The Red brake lamp is not triggered for RABS issues so something else is triggering the Red lamp under live braking. Start with the fluid level check first.
For reference a diagram of the RABS system on these trucks
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