Check-Engine and Speedo-Failure

[Mel_Boss]

Saturday while out on a little run with the Elise-boys, my M100's speedo went inop, including the odometer. Shortly thereafter, the "Check-Engine" light came on and limited my engine speed to 4K-rpm, as advertised in the manual.

Rebooting, turn off/on the M100's ignition temporarily clears the light, but it, invariably, reignites.

I need to find "someone" in the BayArea that can download the error message, which is apparently held in the ECU's memory (somewhere), and who is knowledgeable about Elans.

I am pre-supposing a few things: that the speedo-failure and the CEL illumination are related; that the speedo/odometer are sensor driven (no speedo cable like my type36 Elan); that the problem is not a serious engine problem; that the speed sensor is somewhat accessible (please tell my that it's not behind the dashboard). But I won't know anything until I know the error message.

- Sound familiar to anyone?
- Has this problem come up previously (I didn't see it listed herein)?
- Any recommendation for diagnosis (the M100 not me)?
- Advise?

Many Thanks,
Mel Boss
Danville, CA. USA

[GeoffSmith]

Sounds like a snapped cable to me - I believe the speedo is cable driven and the engine management unit uses a sensor connected to it.

[Doug]

Yo Mel,

you need to check the speedo cable! be sure it is fully seated down into the top filler hole of the tranny

see the Tranny Oil Change write-up for more info on this

this could be the full cause if loose!


read HERE how to diagnose the CEL code with a paperclip at home!

let us know what you find

-Doug

[Candles]

Yes, the sensor known as the Vehicle Speed Sensor has failed, or the drive cable has snapped. It is mechanically driven from the back of the gearbox to the instrument cluster and the sensor is inside the instrument cluster. So, all in all, your nightmares have come true.

Firstly I think you need to ascertain if the drive cable is turning. Jack one wheel up, remove the instrument binnacle cover (black shiny lid on top of the dash), remove the speedo drive and have a look whilst the engine is running with the car in gear (raised wheel spinning). If it isn't turning, the cable has snapped or the plastic gear in the gearbox has died. If it is turning, then you have a problem inside the instrument cluster.

Sorry to not have an easy fix!

Candles.

[Mel_Boss]

Thanks for all the good advise. I will investigate over the next few days, and I will let you all know what I find. I plan to check the speedo cable at the trans first hoping that I can spy something amiss here - loosened perhaps. That would be an easy solution that I can readily solve without any expense. If that connection is good, then either the cable or the sensor requires replacement, and I may opt to bring it to a dealer in the area for repair because it involves ordering a Lotuspart and I don't enjoy tearing into the dash very much, but I'll get an estimate of the time involved from them prior to handing them the project (I'd guess about 2 hrs).

Thanks too for the lead on the excellent techtip on trans oil change and access to the filler.

I sure wish that our cars had been more of a marketing success for Lotus and that the they further developed this design. It's a good design but not fully developed and refined. It would have been interesting to see what would have resulted if Lotus kept it and continued to develope it - awd, v6, better switchgear, redesigned for mfg/service/repair. That's what Lotus did for the Esprit, the Europa and the (original) Elan (which some would argue was a refinement of the Elite). It sure is a great chassis and hangs in there well with the Elises...

[Mel_Boss]

Access to the trans-filler was pretty straight-forward; although, I found the speedo-cable firmly seated in place in the housing. I have attached some photos that may clarify the location and access to this filler for others on the forum.

I made an appointment with BMG in SF for next Monday since "parts" are involved.

Thanks for the advice...

Mel

[L.G.]

Mel Boss,

Got the same problem man, mine isn't the cable for sure. Write up your progress.

Cheers

[Simon_P]

I had exactly the same problem.

The speedo cabe wasn't broken, but there is enough endfloat in the cable/gear so that it didn't engage properly in the gearbox.

There is a small screw/nut that hols a plate that clamps the end of the cable in.

Clean the area thoroughly first - It collects grit which can easily fall into the gearbox when you take the cable out.

The easiest way I found of undoing the nut was to remove the intake hose, then use a 1/4 drive socket with loads of extensions. See pictures

First picture showing all of the extensions - you can just make out the top by the air intake.

Second picture showing cable in gearbox.

More on this subject in the Archive

Regards

Simon

[Mel_Boss]

Thanks for the advice and photos. I found it pretty easy to get access to the Speedo cable inlet to the trans. I took some photos to document the process but was unable to upload them the other day - each under 400kb. I'll try again to attach photos here...
- Loosen hoseclamps and remove the air intake-air hose.
- Remove one 10mm bolt and the strap securing the Rad-reservoir - and gently slide it out to the side keeping the hoses attached!
You'll need "good lighting." The photos show the speedo-cable inlet/trans-filler and the plate w/the 10mm bolt. I made up an ratchet extension with universals that was able to reach the 10mm bolt similar to the one that Simon offered (thank you so much), but I stopped when I saw that the cable was firmly seated. I reasoned that I either needed a new cable or a new speed sensor. I decided to let the Lotus dealer in SF (BMG) "deal" with the problem since one or more parts were involved. And since they would be "in there" anyway, I'd have them change-out the trans-oil (something that hasn't been done in yrs I suspect - I've only owned the car for 3-yrs now) - better done witht the car on a "lift."...
I reduced the photo size, and I'm going to try and attach them again - to this email this time.

Thanks for all the advice. I expect to be back on the road again for next Saturday's run from SanJose to Danville (sponsored by Joel Lipkin and the Golden Gate Lotus Club)

[Mel_Boss]

I could only add one attachment to the former message. Hopefully, the others can be attached to this message...

I've tried for 30 minutes now to add the other two photos, and I've run out of patience. %$#!*#@!
Sorry...
M

[Doug]

it's true you should be sure to wiggle the cable and be sure it is pressed in fully -- as noted by Simon the plastic gear on the end of the speedo cable is small and it's possible that if the cable pops up only a few mm that it can disengage. I remember when doing the tranny oil that you really have to push the gear down and feel it click in -- since you gauge the tranny fill by how far up the gear the oil level goes . . .


PS Mel, who do you trust more to clean the grit around the speedo cable before the shop changes the fluid?? = you should clean up that grit with a properly directed spray of soap, water, and air !!

[Mel_Boss]

Agreed. If I'm successful in posting the photos this time, you'll see that I cleaned around the speedo-cable well. At least the mechanic won't be getting his fingers too dirty

PS Mel, who do you trust more to clean the grit around the speedo cable before the shop changes the fluid?? = you should clean up that grit with a properly directed spray of soap, water, and air !!

[Mel_Boss]

The GOOD NEWS is that the speedo cable was replaced, and all the problems associated with that have been corrected - photo attached shows the shiny new cable at the trans-filler.

THE BAD news is that the inlet (upper) reservoir broke, and I'm waiting on a new one (which is why I missed Saturday's run from Santana Row to Danville).

Thanks to everyone who helped me with this problem.