INSW20 Posted November 20, 2022 Report Share Posted November 20, 2022 Having a hard time getting wheel speed to read. What am I doing wrong? Quote Link to comment Share on other sites More sharing options...
INSW20 Posted November 29, 2022 Author Report Share Posted November 29, 2022 Any ideas? Car is using a completely stock engine and body harness. 1991 MR2 turbo with ABS and cruise control. PNP TST185+ Quote Link to comment Share on other sites More sharing options...
Vaughan Posted November 29, 2022 Report Share Posted November 29, 2022 So "Driven Wheel Speed" is always zero? can you take a log of a short drive and attach it here? Quote Link to comment Share on other sites More sharing options...
INSW20 Posted November 29, 2022 Author Report Share Posted November 29, 2022 On 11/29/2022 at 4:00 PM, Vaughan said: So "Driven Wheel Speed" is always zero? can you take a log of a short drive and attach it here? correct. log attached. thank you! Quote Link to comment Share on other sites More sharing options...
Vaughan Posted November 29, 2022 Report Share Posted November 29, 2022 Try again with the DI 3 Pullup Resistor set to ON please Quote Link to comment Share on other sites More sharing options...
INSW20 Posted November 29, 2022 Author Report Share Posted November 29, 2022 I'll try that and report back. Thank you! Quote Link to comment Share on other sites More sharing options...
INSW20 Posted December 1, 2022 Author Report Share Posted December 1, 2022 That appears to have mostly fixed it. Is it normal for it to jump around quite a bit? It seems like when wheel speed approaches 40mph it goes wild. Wiring issue? Quote Link to comment Share on other sites More sharing options...
essb00 Posted December 1, 2022 Report Share Posted December 1, 2022 what type of speed sensor do you have connected to it DI 3? Reed switch from gauge cluster? Quote Link to comment Share on other sites More sharing options...
Vaughan Posted December 1, 2022 Report Share Posted December 1, 2022 If it's pre 92 (JDM or pre 93 ADM) it will be a cable speedo to the cluster and an electronic from the cluster to ECU, if it's newer then it's hall effect from gearbox and then an altered signal from cluster to ECU. I'm not 100% on what it uses to convert mechanical to electrical but it could absolutely be having trouble with cable friction and/or mechanical to electrical conversion if it is an earlier car. It's also pretty erratic all the time which is a good sign something isn't quite right. Quote Link to comment Share on other sites More sharing options...
INSW20 Posted December 1, 2022 Author Report Share Posted December 1, 2022 Yep, it's an earlier car. It has a 3 wire sensor (I assume hall effect?) that's used for the cruise control speed sensor on the OEM setup. The sensor goes between the mechanical sender and the cable that goes up to the cluster. I'll look for mechanical issues and cable friction problems on it. Thank you all! =) Quote Link to comment Share on other sites More sharing options...
Vaughan Posted December 2, 2022 Report Share Posted December 2, 2022 The 3 pin cruise sensor is only used for cruise control but if the cable setup is in a bad way you could theoretically wire it up to the ECU as well and calibrate the ECU to suit. The Power steering does use the speed signal from the dash though so improving that is still a good idea. On my car I installed a later gauge cluster (needed different plugs) and ran a hall sensor from the gearbox to the ECU with the ECU sending the speed to the gauge cluster speedometer so that I could correct for different wheel sizes. ST18X Celicas have a mechanical to electrical conversion on the gearbox that screws onto the MR2 gearbox too or later gearboxes (with the better synchros and lsd diffs) have hall sensors in them with no provision for a speedo cable. INSW20 1 Quote Link to comment Share on other sites More sharing options...
essb00 Posted December 2, 2022 Report Share Posted December 2, 2022 The speed reading spikes are caused by high frequency noise being picked up by the DI. Try this simple low pass filter circuit below (just if you have some electronic parts lying around). This solved similar problem on mine (though on G4x). INSW20 1 Quote Link to comment Share on other sites More sharing options...
INSW20 Posted December 2, 2022 Author Report Share Posted December 2, 2022 21 hours ago, Vaughan said: The 3 pin cruise sensor is only used for cruise control but if the cable setup is in a bad way you could theoretically wire it up to the ECU as well and calibrate the ECU to suit. The Power steering does use the speed signal from the dash though so improving that is still a good idea. On my car I installed a later gauge cluster (needed different plugs) and ran a hall sensor from the gearbox to the ECU with the ECU sending the speed to the gauge cluster speedometer so that I could correct for different wheel sizes. ST18X Celicas have a mechanical to electrical conversion on the gearbox that screws onto the MR2 gearbox too or later gearboxes (with the better synchros and lsd diffs) have hall sensors in them with no provision for a speedo cable. Ah, looking more closely at the diagram, I see it now: Another question, do we know what kind of signal is created by the cruise sensor if I wired that directly to a DI? 13 hours ago, essb00 said: The speed reading spikes are caused by high frequency noise being picked up by the DI. Try this simple low pass filter circuit below (just if you have some electronic parts lying around). This solved similar problem on mine (though on G4x). Very interesting! I'll see if me and my friend (his car is having the issue, mine is in pieces still) can get that done. Thank you!! Quote Link to comment Share on other sites More sharing options...
Vaughan Posted December 4, 2022 Report Share Posted December 4, 2022 On 12/3/2022 at 10:50 AM, INSW20 said: Another question, do we know what kind of signal is created by the cruise sensor if I wired that directly to a DI Most likely just a hall affect style square wave. You would probably want the DI pullup off if you tap into the cruise signal. INSW20 1 Quote Link to comment Share on other sites More sharing options...
INSW20 Posted December 4, 2022 Author Report Share Posted December 4, 2022 27 minutes ago, Vaughan said: Most likely just a hall affect style square wave. You would probably want the DI pullup off if you tap into the cruise signal. Perfect, thanks again for the help! Vaughan 1 Quote Link to comment Share on other sites More sharing options...
INSW20 Posted January 8, 2023 Author Report Share Posted January 8, 2023 To close the loop on this one, I wired in my cruise sensor to DI4, and ended up turning pullup On to get it to read, for anyone else considering doing this. Now I just need to calibrate against GPS. So far so good! Quote Link to comment Share on other sites More sharing options...
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