05 F150 automatic any ideas as to where the sensor is located

 

It's in the rear axle, it's called a speed sensor.
It feeds the signal to the ABS module, then the ABS module sends it to the PCM, then PCM sends it to the instrument cluster.

 

It USED to be in the rear axle. NOW it's on the output shaft of the transmission. The one on the rear axle is only used for ABS. If you don't believe me, try unplugging the one on the rear axle. Your speedometer will still work and your transmission will shift fine, unlike the pre-2004 Fords.

 

Don't think so, there are 2 speed sensors in the trans but they don't operate the speedo.
If you disconnected the rear axle speed sensor and the speedo still worked the ABS module was using the front speed sensors to get the info to send to the PCM.

 

Think again. I didn't have any ABS sensors reading anything at the time I did this. They were plugged in but merely hanging near the axles because the 54 and 108 tooth trigger wheels didn't exist yet on the '78 bronco I'd swapped everything into.

Let's see what the factory Ford manual has to say:

"Output Shaft Speed Sensor

The Output Shaft Speed Sensor (OSS), provides the Powertrain Control Module (PCM) with information about the rotational speed of an output shaft.The (PCM) uses the information to control and diagnose powertrain behavior. In some applications, the sensor is also used as the source of vehicle speed. The sensor may be physically located in different places on the vehicle, depending upon the specific application."

 

Have noticed similar discrepencies.
Checked speedo out with GPS.
Seems like MPH is a bit fast,(70 on dial is 66 0n GPS);yet the odometer is pretty much right on. (+-1% in 300 miles.) ?.

 

Read it closely "in some applications" The text you quoted is probably at least 10 years old and is generic, it has been copied over and over to save time putting the manuals together..

This is from the 05 FSM on speedo operation in a 05 F150.

Gauges

Speedometer

The instrument cluster receives the vehicle speed sensor (VSS) signal which originates in the ABS module and is transmitted to the PCM over the communication network. The PCM monitors the VSS input and sends it to the instrument cluster over the communication network. With the VSS input, the instrument cluster provides the speedometer with a corresponding pointer movement.

 

Yes I've seen that in the manual as well, but I go back to my original statement. I had zero inputs from the axles yet my speedometer accurately read the vehicle speed. Furthermore using my laptop viewing the vehicle speed real time directly from the cpu gives a slightly different speed than the individual front wheels and rear axle. It's simply taken from the output shaft and calculated from the axle ratio and tire size.

Also the statement I copied came from a 2004 FSM. Is there some reason why the verbage you found could not have simply been regurgitated from previous years as well?

We can theorize and quote manuals all day but it won't change the fact that my 2004 F-150 gets the speedometer signal from somewhere else than the axle sensors. Like I said the first time, if you don't believe me, try it.

 

So you had zero input from the rear and the front speed sensors?
By the way my original posts on this was from memory, memory of fixing them and what the electrical engineers told me at work.
It very well could default to the trans output speed sensor but I doubt it. But hey I've been wrong before.

 

Exactly. I'd been working for over a year on getting the transmission, motor, dash, steering column, ducting, wiring, radiator, you name it, installed in this old '78 bronco. Once I got the rear driveline installed I realized I could actually drive this beast around but figured that the speedometer wouldn't register and the transmission would shift horribly just like all the 90's Ford trucks do when they lose the rear axle sensor. I didn't have a clue how I was going to get a signal off the front wheels at that time, but I wasn't going to let it stop me from testing how the rig felt with this new 5.4L under the hood. To my complete suprise as I pulled out of the driveway the speedometer worked fine and the transmission shifted fine. I did eventually get a trouble code that put the vehicle into limp mode because the ABS wasn't getting any inputs. I agree it's possible the cpu simply switches to the output shaft sensor when the ABS isn't inputing, but I would expect some delay while the cpu realized the ABS sensors and the output shaft weren't agreeing with each other.

Do you work with electrical engineers from Ford? If so I'd love to pick these guy's brains about disabling my ABS. See my project at: http://home.comcast.net/~qcrispin/bronco/

or search for Quint's bronco on google.

Reddslate, are you trying to change your speedometer reading or something? Be aware that the computer compares the inputs from the front and rear wheels. If they differ enough you'll get an error suggesting your tire sizes are off or something.

 

ok from this post, i am trying to find the vehicle speed sensor wire to tap into for my navigation. which wire should i be able to tap into?

seems kind of hoopty to have to go all the way to the transmission or rear axle for a speed sensor wire. isn't there maybe one in the cab?

 

What exactly to the directions for your navigation system say?

 

my nav says to just tap into a speed sensor wire nothing else!

 

Look in your radio harness... If my memory serves me correctly it is a gray/black wire. Some have it...some don't.

 

thanks, i'll give that wire a try!