Speed sensor failure

Wondering how your progress is coming. After Christmas I had taken my truck to QC service center in Charlotte because I had yet even had a computer hooked to the thing. I needed that ruled out. I was told that the unit is receiving the core data from the ecm so it’s not in the wiring to the QC unit. Since there was no issues there CAT reflashed the ecm with there latest pack for my ecm unit.

I picked it up today and this did nothing for it. My next step is to replace one of the sensors on trans. I had replaced one yrs ago because dash speedometer quit working. Gonna replace the other and see what from there. Looking from the rear, forward at the out shaft of trans, one sensor (one I’ve replaced) sit about 10:00 to the driver side. Another sensor (I believe is other mileage/speed sensor) sits about 12:00 with wiring running up passenger side, across trans to ecm.

I’ll try and update if this does it. This some aggravating s&$+!!!

 

Just keeping in touch and updating as I go I guess. If you don’t remember, I mentioned that there are two sensors on back of trans: on at 10:00 and one at 12:00. I bought (I thought both) two sensors. They were both the same and guess what. They are not.

Ok the one at 12:00 is has a pigtail with a rubber, male and female end. The one at 10:00 has a “weather” plug with a lot locking clip. The one at 10:00 is the one going to the ecm. The other, the 12:00, goes to dash speedometer and odometer. Peterbilt said that if replacing the 10:00 doesn’t fix, then I need to test the ohms from sensor to ecm, which that one does go to. I also got an image from Peterbilt of the wiring diagram to ecm. If wires are bad, I can just splice and bypass to sensor.

That’s where I am at this point. Change other sensor in morning and test wiring. So...

Just figured I might say something that may trigger an idea on you end

 

Well I think I have figured mine out. I changed both speed sensors on back of trans. I changed the second yesterday witch ended up being the one that went to the ecm. My cruise was still not working and I don’t think this is what ended up fixing it in the end. On my Pete the cruise control in located on my shifter. The wiring harnes of course travels down the stick to top of trans, and then to the ecm. One of the wires had been spliced a couple of times. I took those out and cleaned them up. I drove down the road and suddenly my cruise was working after 15 yrs (lol). When I had stopped, for the first time, my eld was recording mileage.

I do believe that the issue was in the wiring to my cruise control that was keeping my ecm recording mileage. F’d up but I believe so.

I can not remember what vehicle you were working on but I found out that on some model trucks there is an oil pressure valve in the airline behind the air valves parking brakes. This valve has two wires to it and this activates or enables cruise when brakes are released. Thought that may help.

Good luck to you

 

2005 freightliner Columbia I replaced the harness completely