ECU broken or other fault?

[peter123]

It appears that my ECU may be kaput.The CEL light stays on when the engine is running, and i cannot put it into diagnostic mode or service mode using the paperclip method, also i have tried Elanscan and just keep getting Bad echo (sent:F4 56 01 B5 received C0 00).
I did get a scan to work a few days ago that i have saved but since then nothing.
Is there any way i can check if it is the ECU?

[peter123]

I disconnected the battery last night and reconnected it today to see if that helped, well it seemed to, so i started the car and the CEL light went off , so i thought i would try the paperclip method to see if it would go into diagnostic mode so i turned the engine off put the ignition back on and put the paperclip in the ALDL and bridged the two wires, while i was doing this i heard what sounded like a solenoid clicking from somewhere under the plenum,it kept doing this until i removed the paparclip(the CEL did not flash when the paperclip was in place) I started the the engine again and the CEL stayed on
I have read the manual and it says the idle air control valve is fully extended when in diagnostic mode,could it be this that is causing the problem by not extending due to it sticking or something?

[lotusflasherman]

Purpose of the IAC is to control engine idle speed (tickover) at about 950 rpm. If it's playing up your tickover won't be correct.. is it?

There's a bit in the EMK Manual about allowing about 10 seconds, if I remember correctly, between switch off and battery disconnection to allow it to reset to 0 and count up to it's park position or it gets confused.. (usually take longer than that to get to the battery anyway). When you have had the battery off it looses the memory and has to go through a reset procedure so there will be some clicking until it has sorted itself out. If it hasn't parked properly I think you turn Ignition On and Off and wait 10 seconds for it to park in the correct place and it will be clicking during this..

[peter123]

The idle speed is a bit high about 1100-1200 rpm and it fluctuates slightly also.
The only time i heard the clicking noise was when i put the paper clip in the ALDL i tried to find out where the noise was coming from and it was somewhere under the plenum near the throttle position sensor, and it stopped making the noise when i removed the paper clip, i assume the IAC is somewhere in this area but i can't see it.

[alan e]

I may be wrong but don't you fit the paper clip and then switch on the ignition you will then get 12 flashing 3 times before any faults show.

[peter123]

i just did what i have read somewhere in wiki, not tried putting a paper clip in first maybe i have got it the wrong way round. But it seems like i am not the only one who has had this problem.
viewtopic.php?f=38&t=24435&p=308525&hilit=diagnostic+mode#p308525

[Rambo]

From memory, I'm fairly sure it works either way but will check over the w/e

Normally though, I put the paper clip in first.

PS In over 15 years of owning 3 separate M100s I've never ever had an error code. Is that good luck or what ?

[lotusflasherman]

The idle speed is a bit high about 1100-1200 rpm and it fluctuates slightly also.

That's not right, too high. EMK Manual Page 30 deals with Idle Speed Error that may be IAC playing up or being unable to adjust for other problems. IAC position doesn't generate an Error Code for ELC but it's position is logged in Elanscan and you can plot IAC Position against Time to see what it's doing.

First thing I'd do is check all vacuum hoses for any splits allowing a leak into the plenum and then try unplugging electrical connection to IAC to see if anything changes...

[Rambo]

Your idle speed is about 15 - 20% too high

950 RPM from memory

[lotusflasherman]

Purpose of the IAC is to control engine idle speed (tickover) at about 950 rpm. If it's playing up your tickover won't be correct.. is it?

Keep up Mark ... look further up (but at least your memory is still good )

[Rambo]

Sorry Phil. I hadn't read your post 1st

3/10. Must do better

[peter123]

Thank you for the help it is very much appreciated.
Once again i disconnected the battery overnight, i then put the ignition to on and rotated the throttle valve 5 times to fully open then closed, turned the ignition off, removed the key and waited 40 seconds,(viewtopic.php?f=33&t=24030&start=40) i then started the car and the CEL went out, idle was still a bit high, just over 1000rpm, checked round all the vacuum pipes as suggested by Phil, couldn't find anything so i removed vacuum pipe from the plenum and revs increased slightly, replaced vacuum pipe and the unlipped the IAC wiring connector with no change in rpm. Replaced the IAC connector, again no noticable change in revs. Then i put the paperclip in the ALDL and the CEL started flashing and revs dropped which was great as i have not been able to get this to work , I then set the base timing which wasn't far out, revs increased to just under 1000rpm. Removed the paperclip, revs changed slightly but were about the 950 mark. Then i turned the ignition off, restarted the engine and the CEL stayed on and revs up to about 1500 RPM at idle.

[lotusflasherman]

CEL on - so what's the Error Code ?

[alan e]

Don't take this the wrong way but I think you may need to look on youtube under Lotus Elan m100 engine check light, it will show you how to read fault codes.

[peter123]

Today i seem to have maybe got a little closer to the problem or not.
Again last night i disconnected the battery as i could not get elanscan to get any readings, i could also not get the paperclip method to work, the CEL just stays steady.
This morning i re connected the battery started the engine no CEL, engine running smooth and about 1000rpm idle speed .
I then thought i may aswell try the paperclip just to see if it would work, and it did, CEL doing it's 1 flash then 2 repeatedly, no faults, again like before when i tried this i could hear the ticking noise coming from the IAC so i disconnected it and the ticking noise stopped.
I then removed the paperclip and connected via elanscan and that worked I got two saved logs one with the IAC disconnected and another with it reconnected.
I then turned the engine off and re started it, CEL stayed on and i could no longer connect elanscan so i tried the paperclip and this does nothing either the CEL just stays steady.
I am not sure what to do next, when i get a CEL i cannot read any faults by either elanscan or paperclip, if i disconnect the battery for a while it loses any stored fault codes but at least after reconnecting the battery the car seems to run fine and i can use elancan or the paperclip which show no faults, but then when i restart the engine again the CEL stays on with the engine running a little rough and higher idle speed.
Thanks Alan for the youtube link, but as you can see i can't get any fault codes when i have a fault!!

[lotustonybassplayer]

I believe if the CEL is on permanently the car has gone into limp home mode . It happened to mine earlier this year turned out to be the CAS in my case.
On my elise and my clio when I had a constant CEL warning, it tuned out to be the coil packs in both cases.

[peter123]

i have some new coils and leads on order hopefully they should be here today, i will see if they help.

[peter123]

Could somebody please look at the Elanscan log i have done today to see if there is anything obviously wrong that could be causing the fault i keep getting. I have had a look but not really sure what i am looking for.

21817.rar

This download was done with the car idling with the occasional revving up whilst static in the garage.

[Fredjohn]

Peter
Shouldn't an Elanscan file be an ecu file not rar? I couldn't open your attachment with my Elanscan software.

[peter123]

Sorry about that I compressed it using winrar,I will upload the normal file tomorrow when I can get back on the computer.