Digsy Posted March 23, 2007 Share Posted March 23, 2007 All, Looks like my car has developed the annoying code 42 problem due to a dodgy odometer (as reported on here severel times in the past). I've been reading all about the workaround where you hotwire the speed signal output (blue/red wire) direct to the speed signal re-broadcast wire (pink) to bypass the buffering circuit in the odo. This seems to cure the problem for most people. Just a quick question: Does the odometer simply buffer the signal or does it re-shape it (sawtooth to square wave, for example). Cheers, Quote Link to comment Share on other sites More sharing options...
JustGav Posted March 23, 2007 Share Posted March 23, 2007 Now this has to be one of the better questions I have seen in a long time actually... Without actually knowing I would have to agree that it would probably do some cleaning up of the signal since it has come from a 'noisy' engine area into the car.. Anybody have a 'scope handy who would be willing to do a test? Quote Link to comment Share on other sites More sharing options...
Digsy Posted March 23, 2007 Author Share Posted March 23, 2007 I'm pretty sure I've read somewhere that there is some pulse shaping, yet bypassing this doesn't seem to make any difference for many people. I was wondering whether this was because most people have a speed delimeter somewhere in circuit which does the re-shaping itself. Annoyingly I used to have access to a scope, but I don't anymore. Quote Link to comment Share on other sites More sharing options...
JustGav Posted March 23, 2007 Share Posted March 23, 2007 The ecu must have some allowance via smoothing circuits for a noisy signal, and I'm guessing bypassing the odo buffer just makes it work that little bit harder, however going over the tranny tunnel area will introduce some noise, so the ECU will have to work a lot harder and will probably get the odd bad signal... Quote Link to comment Share on other sites More sharing options...
Guest ol27 Posted March 23, 2007 Share Posted March 23, 2007 I was getting code 42 and a flashing overdrive light at a certain speed on my 93 non turbo auto, I did the hotwire workaround as mentioned above and ive had no trouble at all since then. (about 4 months now) My car has no de-limiter and is still reading in KM with the 110mph clocks but ive had no other codes or running problems since doing this. I don't have a scope tho i'm affraid. Hope this helps guys. p.s. excellent forum btw Quote Link to comment Share on other sites More sharing options...
GLENN STONEHAM Posted March 23, 2007 Share Posted March 23, 2007 I was getting code 42 and a flashing overdrive light at a certain speed on my 93 non turbo auto, I did the hotwire workaround as mentioned above and ive had no trouble at all since then. (about 4 months now) My car has no de-limiter and is still reading in KM with the 110mph clocks but ive had no other codes or running problems since doing this. I don't have a scope tho i'm affraid. Hope this helps guys. p.s. excellent forum btw DITTO my auto gear changes N to 1st & 1st to 2nd were playing up at times as well and that has been cured also. Quote Link to comment Share on other sites More sharing options...
jazz1 Posted March 23, 2007 Share Posted March 23, 2007 how do you find out these codes or problems? Quote Link to comment Share on other sites More sharing options...
GLENN STONEHAM Posted March 23, 2007 Share Posted March 23, 2007 For most of us the warning lights start to come on, usually intermitantly , often when accelerating hard and at a certain speed sfor some about 60 ish MPH but other times as well. In response we start reading any fault codes that come up . see this http://www.mkivsupra.net/vbb/showthread.php?t=35920 The common one is code 42 & it seems this is usually not a speed sensor problem as such but an interupted signal in the odometer circuit. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted March 23, 2007 Share Posted March 23, 2007 Bizzarre New member more adept at using the search than an old hand Quote Link to comment Share on other sites More sharing options...
Digsy Posted March 23, 2007 Author Share Posted March 23, 2007 I was getting code 42 and a flashing overdrive light at a certain speed on my 93 non turbo auto, I did the hotwire workaround as mentioned above and ive had no trouble at all since then. (about 4 months now) My car has no de-limiter and is still reading in KM with the 110mph clocks but ive had no other codes or running problems since doing this. I don't have a scope tho i'm affraid. Hope this helps guys. p.s. excellent forum btw Just to clarify, do you have any kind of speed signal converter fitted at all? Even one to just convert your speedo reading? Quote Link to comment Share on other sites More sharing options...
Guest ol27 Posted March 24, 2007 Share Posted March 24, 2007 Just to clarify, do you have any kind of speed signal converter fitted at all? Even one to just convert your speedo reading? I'm almost certain there's no converter fitted, its got the 110mph clocks which i'm guessing are original equipment for the n/a auto? the mileage and trip computer counts up in km's (getting about 80km from £10 of super!) and it's limited to around 110mph. When I removed the dash all the wiring in and around the speedo area looked stock to me, I did'nt see anything that looked like a converter/de-limited (i've fitted one before on my old gto tt) If there's anywhere else it could be fitted let me know and i'll go take a look Quote Link to comment Share on other sites More sharing options...
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