Guest Flotilla Posted March 22, 2012 Share Posted March 22, 2012 Hi, So I was driving along and the warning light/engine warning light came on intermittently, on for a couple of minutes then off for a couple etc. Got home and checked the diagnosis code which gave out a code 42, which from reading the chart is a 'vehicle speed sensor circuit' fault and not as previously thought 'the answer to the ultimate question'! The car itself is running absolutely perfectly as far as I can tell. Anyone any ideas as to what the most likely problem is/What is the speed sensor circuit? Thanks Quote Link to comment Share on other sites More sharing options...
The-Plethora Posted March 22, 2012 Share Posted March 22, 2012 Do you have a Jspec car running a speed converter? Quote Link to comment Share on other sites More sharing options...
mellonman Posted March 22, 2012 Share Posted March 22, 2012 does you car have abs, had a similar one with a abs sensor Quote Link to comment Share on other sites More sharing options...
Guest Flotilla Posted March 22, 2012 Share Posted March 22, 2012 It is J-Spec yes. I'm guessing the converter is converting from km to miles on the odometer? Sorry, fairly new to my Supra Quote Link to comment Share on other sites More sharing options...
Digsy Posted March 22, 2012 Share Posted March 22, 2012 It could be the speed signal converter going bad or a dodgy installation but there is a common problem with Supras in that the circuit board that the speed signal goes to can develop dry joints which throw up the same fault code. This circuit board takes the speed signal from the sensor and buffers it, and then re-broadcasts it to all the speed-sensitive systems around the car. I did actually datalog the signals going in and out of the circuit board and it was clear that the signal going in was clean but the one coming out kept dropping out. Unfortunately I took the pics on a camera phone but lost them before I could post them up. I had the code 42 error for literally a couple of years and as you say it ran normally the whole time apart from occaisionally I would get an abrupt shift from the auto box (presumably because it could not work out what speed the engine was doing). Sometimes I would get a flashing OD/OFF light too, meaning the transmission had got confused. If this is the case then the simplest fix is to replace the circuit board. Finding on on here shouldn't be too hard. The downside is that your odometer reading will no longer match your car unless you have it clocked somehow (not sure if this is even possible). There is another workaround whereby you simply short circuit the speed sensor input direct to the output. Many people have said that this works fine but I was loth to try it in case it overloaded the current capability of the sensor output. Quote Link to comment Share on other sites More sharing options...
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