WKelley Posted November 30, 2022 Share Posted November 30, 2022 (edited) OK, my car has gremlins. More than a few. This one is getting on my nerves. As with all the issues with my car, this happens randomly and not very often. Usually within a minute or 2 it reads again and the self locking doors do their thing. It's obvious that there's no speed signal somewhere, but where to look? Speed sensors are big bucks for these cars, $150+. My car also has symptoms of a failing engine computer, but I don't have a scan tool to diagnose that problem either. I am relying on the Torque app and an ELM327 bluetooth device (old one too). Does the speed sensor first report the the engine computer and then to the actual speedometer? Any info on this system would help. I have physically unplugged the speed sensor and sprayed Deoxit in the connection already, no corrosion there. Edited November 30, 2022 by WKelley 0 Quote Link to comment Share on other sites More sharing options...
Grampy Posted December 1, 2022 Share Posted December 1, 2022 (edited) The computer gets the "speed" signal 1st (not like the old days when a cable spun a magnet). If the indication is "flakey" but the computer is seeing the actual speed (you can verify with your "torque" app, you can use it as the speedometer directly from the ELM327 gizmo, my brother did for about a year in his '04 Silverado) I haven't heard of FORD having many recent speedo issues, but GM (trucks) have a long and poor history of dash inst's goin "bananas" so much so there is an industry of electronic DIYers that rebuild GM inst panels for about $100 (that's what my brother eventually did). You have options, might I suggest www.car-part.com, to find a local junkyard replacement speedo if you diagnose it to the inst panel or maybe even that "$150 speed sensor you mentioned. I have had success over teh years keeping my vehicles alive w/ "used parts". Back in the day I bought a junk yard speedo for my son's '94 F150 XL (his XL was a manual transmission, yet the XL DID NOT come with a tach, so I got him one out of an XLT w/ a tach for christmas. My daughters '02 Mountaineer teh speedo would stick @ 60 MPH periodically, she didn't care till she got a ticket. Stopped she showed the cop it was still at 60, she thumped it went back down, I got her a junkyard replacement.. , In court he cop said he remembered her and it was the "da**est" thing it was really stuck @ 60, she showed the judge the receipt and said my Dad replaced it for me, judge let her go w/ no fine, since it was fixed. I don't have my 2010 shop manuals where I am right now, I can access them in about 2 weeks.. If you need help researching the manuals/wiring diagrams in a couple of weeks drop a message. Edited December 1, 2022 by Grampy 0 Quote Link to comment Share on other sites More sharing options...
WKelley Posted December 1, 2022 Author Share Posted December 1, 2022 Torque will show a GPS determined speed, but the computer reads 0. The proof of that is the auto door locks don't work unless the speedometer works. The needles do their sweep normally at startup, it doesn't seem to be the issue. I'm also surprised it does not set ABS or other codes when I'm driving yet no speed showing. To me this is another sigh the ECU is either not reading or not seeing the speed sensor. I don't mind spending the $150 if that's the issue, I guess I need to have my engine computer tested as well, my car has a random start/stall issue which again it never sets codes. 0 Quote Link to comment Share on other sites More sharing options...
Grampy Posted December 2, 2022 Share Posted December 2, 2022 Good luck, the good news it isn't the speedometer (eliminating things that are NOT the problem is good troubleshooting) the bad news it isn't the speedometer (speedometer is an easy fix) 1 Quote Link to comment Share on other sites More sharing options...
WKelley Posted December 22, 2022 Author Share Posted December 22, 2022 Small update, I was wrong about Torque reporting GPS speedo. It does use the reading from the speed sensor. Checked it yesterday when it acted up and it read zero speed on Torque as well. I am still somewhat baffled why the car doesn't throw a code as I would expect the ABS/traction control to freak out because the wheel speed sensors are working but there is no speed input from the transmission. I am leaning towards that sensor more and more, time to start shopping.... 0 Quote Link to comment Share on other sites More sharing options...
akirby Posted December 25, 2022 Share Posted December 25, 2022 Pretty sure abs and tc only look at the relative speed of each wheel to the others and not the vehicle speed. Probably the sensor but try to check for loose or broken wires first. 0 Quote Link to comment Share on other sites More sharing options...
WKelley Posted January 7, 2023 Author Share Posted January 7, 2023 (edited) OK, this is happening very frequently now. I set up an experiment: I have the Torque app showing GPS speed and OBD reported speed. About a 4KM/h differnece between those 2. Here's the real twist, the speedometer is reading 4-5KM/h slower than the OBD reported value. So to make this clear, the GPS speed is 4KM/h higher than the OBD reported speed. The speedometer is 4-5KM/h lower than the reported OBD speed. I ran this experiment on flat level ground with cruise control holding it at a steady speed. I varied the cruise between 80KM/h to 100KM/h and the differences in the reported 3 values were consistently the same spread of values. Why would the speedometer read lower than the OBD value? Edited January 7, 2023 by WKelley 0 Quote Link to comment Share on other sites More sharing options...
WKelley Posted January 11, 2023 Author Share Posted January 11, 2023 Now I have an occasional stalling issue when the speedo is not working. Seems like my problem is getting progressive and pointing towards engine computer. 0 Quote Link to comment Share on other sites More sharing options...
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