ABS and Harsh Downshift

[countrycorey]

Over the last 6 months or so, I have been getting an intermittent ABS light that I can't trace out. It would come on and clear on its own about once every other week.

Fast forward to this week and I've had the following occur:
1. I get the ABS light every day, sometimes clearing immediately and other times it takes a few keystrokes to clear. It usually comes in when I lift off of the throttle to coast but before I apply any brakes.
2. I can feel the ABS module activating under very light braking.
3. I have felt a hard/harsh downshift as I'm slowing/coasting to stop (felt like I got rear ended). This happened once yesterday and twice today, both days on the way home and both days 4. Was slowing down for a speed bump leaving work yesterday and had the truck jump to the drivers side like the drivers side brake had locked up.

Recent brake work performed was new pads and Rotors, CV shafts installed in January.
I replaces the rubber hoses and flushed the fluid in 2018.

I verified the reservoir is full.

I pulled the following codes this afternoon

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[2004LB7]

clean and or replace the ABS sensors at the front wheels. sand down the rust that forms under the sensor and make sure the tone ring is clean and clear

 

[Ron Nielson]

Attachment may help if the sensors don't fix the problem.

Interesting item from the attachment:

Conditions for Setting the DTC
• The brake pedal is sensed as applied for 6 minutes.
• The vehicle speed is greater than 21 km/h (13 mph).
AND
The DTC C0161 00 can be set if the brake switch is applied while accelerating.

Sounds like there may be a brake switch problem. Cheap to replace and doesn't cost much.

 

[countrycorey]

clean and or replace the ABS sensors at the front wheels. sand down the rust that forms under the sensor and make sure the tone ring is clean and clear

Is that an issue with "new" bearings/Hubs? I know anything is possible, but this is the 3rd set of Hubs and the first time I've seen this happen.

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[countrycorey]

Attachment may help if the sensors don't fix the problem.

Interesting item from the attachment:

Conditions for Setting the DTC
• The brake pedal is sensed as applied for 6 minutes.
• The vehicle speed is greater than 21 km/h (13 mph).
AND
The DTC C0161 00 can be set if the brake switch is applied while accelerating.

Sounds like there may be a brake switch problem. Cheap to replace and doesn't cost much.

I know I had an issue previously where the shift interlock solenoid failed and the dealership forgot to plug in the harness to where the brake switch would pick up and allow me to drive the truck but would not allow cruise to be set, so could the code be left over from that?

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[Ron Nielson]

I don't know if that code could come from a failure to plug in the harness. But if the brake switch indicated that the brakes are applied, you would be prohibited to go into cruise control.

 

[countrycorey]

Update on this issue:

After this condition started, I noticed that my battery cables (relocated passenger battery in the toolbox after installing twin turbo) were hanging down below the body and frame like someone had tried to rip them out. The ABS light and other symptoms had been occurring for a few weeks when I noticed that. After I resecured the cables back up between the body and frame, the condition has not happened again.

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