GrahamV Posted January 23, 2014 Share Posted January 23, 2014 Hi, The ABS warning light has come on and the speedo has stopped working ( plus management light) I have read the diagnostic codes and get P0500 and P0121. From what I have googled, I am guessing it is likely to be a speed sensor but would this be on one of the wheels, or on the gearbox? Would I have both? Also I have looked up the P0121 code and it refers to "Throttle Position Sensor Switch". I have absolutely no idea what this might be. Can anyone shed any light? Many thanks, Graham Quote Link to comment Share on other sites More sharing options...
jeebowhite Posted January 24, 2014 Share Posted January 24, 2014 Basically, the ABS system operates as the speed sensor. It constantly monitors the wheels and relays the data to the ECU which calculates the speed. Given that you have no speed at all, I would say that you may be looking at an ABS Module issue, or a duff sensor. Ordinarily the code reports what sensor is affected, but as its not doing this, I believe either the fuse for ABS may have blown, or the module is the issue. Start off by tracking the fuse and replacing it if necessary. Quote Link to comment Share on other sites More sharing options...
GrahamV Posted January 25, 2014 Author Share Posted January 25, 2014 Thanks very much. That is very helpful. I really hope its not the ABS module as the car is only worth a few hundred pounds and it may mean I have to lose her. She runs really nicely otherwise and has "only" done 45k miles. on the other hand if it is the fuse, that would be a great result! Any idea which fuse it is, or is there somewhere where I can find a list of the fuses? The price of speed sensors on the wheels looks reasonable. Is there also one on gearbox/transmission? I assume there is no way of telling which is faulty - I guess its just trial and error. I have read to test they should show about 1,000 ohm resistance Many thanks for the post - Graham Quote Link to comment Share on other sites More sharing options...
jeebowhite Posted January 27, 2014 Share Posted January 27, 2014 Hi Graham, Best bet is to buy Ford branded sensors, you will end up with a world of trouble trying to use one aftermarket amongst a load of Ford! As for the fuse diagrams, I dont know of a reliable source, but a quick search on google should come up trumps! Ordinarily the error codes would shout "here I am" (they did on my car last year!) as I tracked down the issue to the offside front wheel, turned out to be the loom at fault... but if your not getting that, it makes it more difficult... Quote Link to comment Share on other sites More sharing options...
GrahamV Posted January 30, 2014 Author Share Posted January 30, 2014 Hi Sorry for delay in posting back but have been waiting until now to get the use of a more advanced scanner. I had loads of codes, so deleted them all, drove a hundred yards, and did a fresh scan. I got the following reading: C1236 - Speed Wheel LR Input signal missing C1155 - Speed Wheel sensor LF Input circuit failure It seems a coincidence that both front and rear left side have both failed, or am I misunderstanding this reading? Is it possible there is a failure, bad connection where the left hand leads connect to the main unit? I am not sure where to find the main abs unit nor what it looks like! Many thanks for help, Graham Quote Link to comment Share on other sites More sharing options...
Stoney871 Posted January 31, 2014 Share Posted January 31, 2014 The results do seem to point to a common denominator. For both sensors to fail is unlikely. I'd say trace the loom from both sensors and follow back where you can, checking for damage or corrosion. Quote Link to comment Share on other sites More sharing options...
jeebowhite Posted February 3, 2014 Share Posted February 3, 2014 Sounds like the looms as Clive said. I had an issue with my ABS that killed the car, the loom was the fault and the job was done for £55 no further issues since! Quote Link to comment Share on other sites More sharing options...
GrahamV Posted February 3, 2014 Author Share Posted February 3, 2014 Thanks for the postings. I have been playing with the diagnostics tool. It was able to read the speed sensor speeds coming from each wheel. They were identical which I thought was encouraging. And it seems to have cleared the error. The abs light has gone and speedo works fine. I am thinking maybe something was jammed in the teeth of speed sensor and has now cleared? Anyway thanks for the help Quote Link to comment Share on other sites More sharing options...
Stoney871 Posted February 4, 2014 Share Posted February 4, 2014 Dirt and water can interfere with the abs sensors, hopefully your trouble won't re-occur. Quote Link to comment Share on other sites More sharing options...
Jude Fletcher king Posted July 15, 2020 Share Posted July 15, 2020 Mine has done exactly the same. We got a cheap code reader and it said speed throttle problem. The garage have had it for over a week and cannot find a source. They say the computer isn't talking to the ECU? So they don't know what to do? Quote Link to comment Share on other sites More sharing options...
Joshdeb Posted February 10, 2022 Share Posted February 10, 2022 Ford fiesta 2011 1.25 power stering gone light on Traction control light on Speedometer not working Engine management light on . Problem on machine Engine modul ....... Quote Link to comment Share on other sites More sharing options...
unofix Posted February 10, 2022 Share Posted February 10, 2022 If you use FORScan and get the DTC then it will tell you the problem. Most likely you have a faulty ABS sensor on one of the wheels. Could just the wiring to the ABS sensor. Quote Link to comment Share on other sites More sharing options...
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