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  • Name
    Anton Karnaukh
  • Car
    1995 Lotus Esprit S4s
  1. Derek, thank you, but, sorry, how do I swap/invert pins on the ECU?
  2. Hi Filip et al, thank you for your advice. I just found - by rotating the r.h.s. rear wheel by hand (and blocking the l.h.s.) - that Freescan registers the speed up to 3 or 4 mph! So I guess that means that the ECU 'sees' the signal, but - doesn't transmit it to the speedometer. (and BTW the VSS on my car is new). The speedo itself is original, it's a Caerbont unit. I made sure (multiple times) the wiring is connected correctly (both in sync in how it was on the car before the speedo started misbehaving, and in sync with the schematic in S3 chart). So what do you think the problem may be now, and how can I diagnose it further? I was advised to take the ECU out and inspect it - for bad soldering, mini-cracks... Could it be that the ECU itself is faulty (and if so, in what sense? it's just the speedo that isn't working; the rest of the car systems seem to be working OK), and if so, what can be done about that? Please advise, thanks very much for your help.
  3. Filip, thank you. Well, first, I checked continuity between VSS (speed sensor) and the ECU. Now, how do I exactly check what you are suggesting - that the ECU sees the signal (from VSS)? It sounds like you are implying I should run Freescan when the wheels are rotating? That could be achieved by either 1) driving the car and having a laptop with Freescan hooked up (unfortunately I can't do that since I don't have a laptop), or 2) as Derek suggested, jacking up the car and running the engine in 1st gear (that I can do since I have a stationary PC with Freescan). I still don't feel comfortable enough to do the latter, but perhaps I'll finally get to doing it - or trying to rotate the wheel by hand - to see if the speedo in Freescan reacts to that. I tried the latter only to check that there is some small voltage on the VSS contacts (that's 'the beginning of the line'). I also know there is no signal at 'the end of the line': the speedo doesn't receive the signal (even though I had the speedo itself checked by a speedo shop so I know it's working). And also there is continuity between the ECU and the speedo. So it feels like something inside the ECU is either not getting the signal from VSS, or getting it but not passing through to the speedo. Anticipating the outcome, what would be the causes in each case: 1) if Freescan doesn't register speed? 2) if it does? Please advise.
  4. Barry, exactly that happened to me - the VSS threw the code 24. So I ended up replacing the VSS with a new one. No code 24 anymore so far; I guess the old sensor was somehow bad. Derek, yes, I thought about that and actually, with the wheel taken out, tried to rotate the brake disk and saw a multimeter register some small voltage upon rotation. However I measured it only on the VSS contacts. So the next question is: where should I measure the same voltage (when rotating the wheel) on the ECU? The input contacts there are J3-C2, J3-C8. The continuity between them and VSS checked out. The output contact of ECU (towards the speedo) is J2-B8, the continuity between that and the speedo checks out as well. However, as I come to think of if, I never measured the voltage between the output contact (J2-B8) - and the ground, I guess (when rotating the wheel); is that what I should try next? BTW, thanks very much for replying.
  5. Hi Derek, thank you for replying. I thought that too, but the S3 sheet diagram may have some inaccuracies (in general) re: S4s, for example it has a tachometer amplifier that S4s doesn't have, as far as I know... I checked the signal continuity everywhere I possibly could - in the speedo-related wiring/circuits. I guess what you are saying is that I should try to run Freescan while driving (that is, when the rear wheels are rotating) to see if it it 'registers' the speedo, that is, the latter shows non-zero speed; is that what you meant? I'd like to be able to do that, but it may be a problem at the moment: I don't have a laptop, only an old PC with a serial port (via which I connect Freescan), hence I can run it only when the car is stationary. I was advised to try to run the wheels (with the car's rear being up on the stands) with the engine on and at low speed, but I don't feel comfortable doing that yet. Are there any other ways to diagnose this kind of problem? I was told I should get out and open the ECU to try to see if there is any soldering going bad, any (microscopic) cracks etc.
  6. Greetings to All, The speedometer on my S4s is still not working. I ruled out the speedo itself (had it checked by a speedo shop, it's working OK), the connectivity between all known 'external' points, and finally the VSS (vehicle speed sensor) - I replaced it with a new one. So has anybody ever encountered a problem inside the ECU (a burnt circuit, internal cracks etc) that may cause the speedo not to work? Any insight will be appreciated, thank you in advance! Anton.
  7. Hi All, Does anybody happen to have an electric diagram (chart, schematic) for S4s which has the speedometer in it? The Service Manual has only 1 sheet - Sheet S3 in Section ML that ever shows a speedo, and it's for Sport 300. It appears there is no official sheet for S4s. The previous page - Sheet 3 - for MY 95.3Y - doesn't have a speedo, because, as I understand, with S4 (MY 94) and prior SE's (MY 93 and earlier) the speedo was mechanical, not digital. S4s (MY 95) seems to be the only year with the 4-cylinder engine when the speedo became digital. I need this diagram as I'm trying to solve a wiring problem. The speedo on my S4s is not working. I had it checked by a speedo repair shop just now and it's fine. Connectivity from ECU's connector J2-B8 to the speedo's orange wire is fine. Connectivity from VSS (vehicle speed sensor on rear right wheel hub) towards the harness near the ECU is fine. But after that the wires go somewhere, before they reach ECU, so there is no connectivity between that point and ECU - connectors J3-C2 and J3-C8. Sheet S3 shows that the wires from VSS go directly to ECU, but, as I described, I found it to be not true. At worst, I can try to trace that wiring myself, but of course having a true diagram would help! Thanks very much in advance. Anton '95 Esprit S4s
  8. Hi All, Thanks very much for your help! I have some further questions: 1) What's the procedure to check if IAC is working correctly (or not)? 2) Same question re: a procedure for TPS? BTW, I checked that Freescan has some TPS data; at least there is a TPS column in the csv log dump file. Please advise, thanks very much. Anton.
  9. Hi All, As I've got my car back on the road, after a recent engine rebuild etc, everything works OK. However sometimes, when slowing down, before coming to a complete stop, while still in gear, the engine may stumble and stall. I restart the engine, keep driving and all is OK. Before the rebuild I don't recall that happening noticeably. I was told that it may be a IAC (Idle Air Control) valve issue, it may need to be replaced. Can somebody please advise on this problem and if it's related to iAC? I can provide more information on what has been done on the car during the rebuild. However the IAC is original. Please advise, thank you in advance. Anton '95 Esprit S4s
  10. Derek/Sailorbob, Thanks very much for your advice. I already inquired at CIA, will see which range they will confirm (I hope it's 10 - 180 Ohms, Empty to Full as you indicated). I couldn't find that S4s gauge by the CIA part # on their website though. Anton.
  11. Hi All, I'm trying to solve this problem: for the original Caerbont fuel gauge on my Esprit S4s, I need to find a fuel sender that matches its resistance range. Originally I bought a new ISSPRO RA9510 fuel sender as a replacement for the old one, but I bought one with a wrong 'signal' (resistance range) by mistake: -ISS, 240 - 33 Ohm (Empty - Full), according to the info here, for example: I couldn't get it to work, trying all possible connection combinations (and while at that, checked the wiring to be OK). I even suspected the fuel gauge to be faulty and replaced with a new one - same Caerbont unit at the old one. As the resistance range of the fuel gauge must match that of the fuel sender, I need to find out what the range for this Caerbont fuel gauge is. Can anybody please tell for sure? I just heard on Turbo Esprit list that it may be (in fact for all Caerbont gauges) 340 - 30 Ohm (Empty - Full), but I'd still like to verify that. This range doesn't seem to be available at though. Another suspect is -EURO version: 10 - 180 Ohm (Empty - Full). Please kindly advise, thanks very much. Anton '95 Esprit S4s
  12. agk

    The Esprit Registry

    1995 Lotus Esprit S4S Silk red/tan interior SCCFD30C8SHF63023 Anton Karnaukh user name: agk Princeton, New Jersey, USA
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