SHE'S ALIVE: Battery – Reversed Polarity = Fried ECU? -

[roadboy]

That's the oil temperature sensor.

The two solenoids are below there (black cylindrical things) with the blue and brown connectors on them.

HTH

Dan

[Stewart]

That's the oil temperature sensor.

The two solenoids are below there (black cylindrical things) with the blue and brown connectors on them.

HTH

Dan

Thanks Dan. Do you mean lower down on the side of the head? Are they fairly accessible - for a Lotus? Easy enough for a numpty like me to check?

I have been doing a bit of surfing to see if I can find a picture of them or even a price for them but having no luck.

Edit:
Just went back out the car and think I have found them

The brown one looks reasonably accessible not too sure about the blue one. What the best way to get that off - remove the plastic cover from the head first? Also, do I push the metal clips to release? Sorry for all the questions, but after such a rookie mistake I don't want to do any more damage!

[roadboy]

Yup, that's them. Take the plastic plug cover off and you can remove the blue plug.

Push the wire in over with a flat blade screw driver where the notch is on the plug (visible on the brown plug in the pic above) and then pull the plug off.

With the plug removed check the resistance across the two pins on each solenoid. It should be between 6.6 and 8.8 ohms (depending on temperature) if its healthy.

Dan

[roadboy]

Oh, and further to your post on SELOC, one of the circuits that usually gets fried with reverse polarity is the IACV circuit so hopefully the ECU repair will solve this.

Dan

[Stewart]

Dan, much appreciated, thanks. Doesn't look too big a job to test them then. I am sure my dad has a suitable meter for doing so.

Interesting learning about all this stuff, just a pity I've had to go through the pain! I still don't feel that confident that if I get the ECM back "repaired" that all will work, but I really hope so if for no other reason than I feel I have let the buyer down.

[robin]

Everyone can make a mistake - the question is what do you do next. You've been totally honest with your buyer and are doing everything possible to get the car back in shape and ready for them to buy. That's all anybody can ask.

Re: the multimeter - make sure that you check the meter reading with the probes shorted together. It should read zero; if it reads one or two ohms, you can subtract that number from the number you measure; if it reads >10 ohms then the meter is useless for this type of problem.

Cheers,
Robin

[Stewart]

Thanks Robin. I'm not entirely clear on how to check them. Do you mean just lay one terminal from the meter across the two connectors of the solenoid? I imagined that I would need to try and complete the circuit through the solenoid using both ends of the meter?

Autotekelectronics have just called and confirmed a fault which is repairable. Good news and good service (just sent yesterday) but comes at a price -£245!

The girl who called had a very think accent and was hard to understand. They will send a report back with the unit but advised to check fuel system, ignition system and injection system - understandable.

Am I able to check any of these before reconnecting the ECM or will they not do any damage even if there is a problem with the IACV etc?

[robin]

The multimeter has two probes (cables with shiny pointy bits on the end).

To check the function of the ohm meter you should connect one probe directly to the other (not touching the car). For a perfect meter it will read 0 ohms at that point. Typically they read 0.1/0.2 which is also fine. If it reads 10 ohms or more you cannot use it to measure a low resistance like 6-8 ohms because that value is "below the noise floor" as they say. If it's a halfway modern meter it will be fine.

It's possible to check all of the things you mention from the ECU plug using an ohm meter and a couple of bits of wire with stripped ends, but I don't have time now to write up what's needed. If you can wait until the weekend I can post some annotated pictures of the inside of the ECU plugs to show you which pin is which and what test to perform?

Cheers,
Robin (should have left for Oulton Park 2 hours ago ...)

[Stewart]

Robin, as always an extremely helpful post. Thanks for taking the time.

Details on what to check would be very helpful and really appreciated. I wont be touching it until the weekend. I am hoping that my brother will keep right as he was a flight systems tech in the RAF. A guide would obviously help as we have nothing to work to. I do have some wiring diagrams but I think they are just for the 118bhp S2.

P.s.
Probes! I couldn't think what they are called

[fd]

You're just down the road from me, If you're stuck I can bring a good multimeter and check things out, presuming you can determine what actually needs checked

I am perpetually busy, but . . . if you're stuck let me know . . .

Fd

[Stewart]

You're just down the road from me, If you're stuck I can bring a good multimeter and check things out, presuming you can determine what actually needs checked

I am perpetually busy, but . . . if you're stuck let me know . . .

Fd

Fergus, thanks for the offer. I will have a better idea what to check once I receive the ECU back with it's report. What I am trying to determine in the meantime is will I damage anything else by just plugging the ECU back in and trying to start the car? I know blown VVC solenoids will likely re-blow the ECU but not sure about anything else. Perhaps it's impossible to tell and safer to check all main functions?

I will indeed give you a shout if we are stuggling. Thanks again.

[fd]

I suspect there's some internet old wifes tale-ery about the 'blown' solenoids idea . . . but that's just a hunch . . . anyway if you believe in voodoo and can't verify the solenoids are OK (which will be simple enough) just unplug them . . . I expect the system will fail safe from an engine mechanical point of view (ie. no different from a jammed solenoid for example) . . . only thing I can think of is if the solenoids have a flyback protection diode built in and it's failed short circuit, but I'd have thought that very unusual . . . the same voodoo probably applies to the IACV stepper, the ignition coil, etc, and I don't expect any of them to be any more likely to have been damaged . . . clearly you cannot disconnect the ignition coil pack and expect it to start . . . but . . . it's a reasonable principle to follow.

[robin]

Here's a PDF that I scratched out in a hurry so excuse format, etc. Please feedback so I can improve ...

http://db.tt/HGSwYiPA

Cheers,
Robin

[Stewart]

OK, managed to check the VVC solenoids and they are spot on, reading 8 ohms. We just got in from the garage after checking these when I spotted Robin's post so went back out to start checking the loom. Please note that I do not have the ECU back so unable to try starting the car at this point.

Here's a PDF that I scratched out in a hurry so excuse format, etc. Please feedback so I can improve ...

http://db.tt/HGSwYiPA

Cheers,
Robin

Robin that is great and has been a huge help. Really appreciated.

My brother and I have now run through all the checks listed and found readings within the ranges suggested by you. All but the IACV performed as suggested.

Idle Air Control Valve Coils
To test these you need the meter set to measure resistance of <200 ohms (200 ohm scale typically).
I don't actually know what the correct resistance values are. I think they should be in the 10-30
ohm range though. Luckily there are two coils and they should be the same!
The relevant pins are 13, 24, 39 and 50.
I think you should see 10-30 ohms between 13 & 24.
I think you should see 10-30 ohms between 39 & 50.
You should see open circuit between 13 & 39, 13 & 50.

Between both 13 & 24 and 39 & 50 we are getting an open circuit and not the 10-30 ohm range suggested.

Between 13 & 39 we are getting 56 ohms, and between 13 & 50 is showing as an open circuit.

Between 24 & 50 is showing as 56 ohms

We have checked the circuit from the ECU loom to the IACV connector and it's complete. We have now removed the IACV to test it using the meter and as suspected we are getting 56 ohms between the external two pins and the same between the internal (middle) twins pins. When using them as pairs i.e a middle pin to the one next to it on the outside we are getting an open circuit.

Does this mean the IACV is knackered? Is is possible that pins in the diagram as numbered wrongly?

Thanks again

Stewart

[robin]

Nope, it means my document is wrong.

The IACV is a pair of identical coils. I thought they were 13/24 and 39/50. They must be 24/50 and 13/39. I also didn't know what sort of resistance to expect - the fact that both coils have 56 ohms makes me think that's spot on.

I'll amend the document tomorrow for future reference - thanks for being the guinea pig

Cheers,
Robin