Have a 2008 F150 4.6L and I'm having a couple of electrical issues. The first is with the cruise control and started about 3 weeks ago. The cruise control will randomly not turn on and when it does it might just randomly turn off. I replaced the brake switch and the cruise control deactivation switch but that didn't fix the issue. I have a Ford scanner, and I verified the controls on the steering wheel all work as expected. A week after the cruise started to work intermittently my ABS light came on. It's throwing a C1230 code for the rear center wheel speed sensor. I replaced the sensor but that didn't fix the ABS. I checked the sensor for voltage and I have none. The wiring at the sensor seems fine but not sure how to check the rest of the harness. Assuming there's a short in the wiring somewhere is there a tool that could track it down? Could the 2 issues be related? Maybe a bad ground etc... Is there a way to check the ABS module itself to make sure it's supplying power to the sensor? With the Ford scanner it reads both front speed sensors but not the back. It lists the back sensors are right/left and not just one. I checked all the ABS fuses and they are all good. Any known issues here? What do you all suggest to further troubleshoot this? Cruise control is nice but I can live without. ABS in Michigan during the winter is almost a necessity so I really need to figure that out above all else.

 

Check the ground wires located next to the CJB (fuse box) behind plastic kick panel as these sometimes rust away.
Are all bulbs in the third brake light working? Shorts or corrosion in third bake light wiring can be the issue. With third brake light removed gently pull on the wire that trails off the the right and look for damage or poor connection.

The video in the following posting goes into a lot of detail as to how to troubleshoot cruise control issues

https://www.f150forum.com/f38/stuck-...558523/index2/
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Do you have access to a set of wiring diagrams for your 2008? If so, page 42-1 shows the circuitry and you have three connectors between the Rear Axle Speed Sensor and the PCM, each of those should be checked.

 

The 3rd brake light isn't work. The outside white lights work but not the middle one. I suppose the bulb could be burned out but I doubt it. Can you post the wiring diagram you're talking about?

 

fix the brake light and your cruise will work and anything else on that fuse.

 

Here are the 2005 diagrams, I would guess this wiring stayed the same 2004 through 2008.

If you Google "2005 f150 wiring diagrams searchable PDF" these should pop up