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

[Stewart]

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

Phew, that's a relief . I am hoping , but not yet convinced, that I may have gotten away within "just" a fried ECU. It will be a really apprehensive re-installation later this week.

Thanks again for taking the time to put this together. I want to say that hopefully the doc will be of use to someone else in the future, but I do hope no one else is as dumb as me and reverses the polarity.

Also, the IACV is a lot of fun to remove To refit it I found a small ratchet ring spanner that was almost the right size to fit the torx bit into so was easier to refit with the threads of the screws cleaned up.

I am now just waiting for the ECU to be returned - hopefully Tuesday or Wednesday. Not sure if I will get it put back together and tested in time for Antoine to book a flight for the weekend, but that would be the ideal scenario. Better not get too excited

[simon]

Every time I see the name Antoine I can't help but think the guy will look like this

[robin]

Why did you remove the IACV?

[Stewart]

Why did you remove the IACV?

We were struggling to get the meter probes onto the contacts to check it correctly so decided to take it off to check it properly. It went on way easier with the right tools and the threads cleaned

[robin]

But you could have measured the resistance from the ECU plug ... oh well

[Stewart]

But you could have measured the resistance from the ECU plug ... oh well

Yeah, we did that but as we couldn't get the readings we were expecting , I decided to remove it to make sure the IACV was ok. I basically didn't want to regret not having checked it as I am just so aprehensive about refitting the ECM when I get it back.

[Stewart]

OK, the ECM arrived back today looking all nice and shiny. Fairly quick service as it was only sent to them last Wednesday.

Just fitted it back into the car and carefully connected the battery (correctly). Signs were positive. No sparks, small chirp from what sounded like a relay or something to do with the alarm/immobiliser.

Turned the key, fuel pump primes, car turns over but will not fire. No sign of trying to start at all. My guess is no spark as there is a faint smell of fuel although not a lot. The only difference is that before the ECM was sent away, I was getting a strange noise from what sounded like relays in the engine bay when I switched on things like the lights.

I had previously checked all the fuses and they were sound.

Any thoughts?


The report that came back with the ECU reads,

This ECU has been tested and found to be faulty. It seems the power supply circuit has been overloaded and damaged the ECU. Please check the fuses to the Ignition Coil and the Injector rail circuits before reconnecting the ECU back to the car. Refurbishment is required. This ECU has been refurbished.
Before connecting the ECU please
Check all 12 volt power supplies
Coming into this unit.
In particular the 12 volt
Supply from the ignition
Switch & the Battery.
This ECU has been tested several times simulating a cold start condition 9 volt engine cranking speed of 200RPM up to 6000RPM at normal running temperature and no faults found. We have enclosed a wiring diagram to help diagnose the missing 12 volt on the vehicle.

[robin]

I'm assuming you checked that the crank position sensor had the correct resistance.

Disconnect your battery, disconnect the ECU.

Reconnect battery.

Turn on the ignition (doesn't matter about immob).

With meter in voltage mode, measure voltage between pins 59 and 54. It should be 12V or higher.

Now using a length of wire connect pin 59 to 54 (be careful not to connect the wrong pins).

You should hear the clonk of the main relay inside the MFRU.

Now measure the voltage between pin 73 and 19. It should be 12V or higher.

Assuming that's correct then the main relay/MFRU is working fine.

Next turn the ignition off.

On the VVC the cam position sensor is a VR sensor much like the crank position sensor. Disconnect battery and measure resistance between pins 16 and 42. I guess it should be 1300 ohms give or take.

Finally check that the voltage between pins 80 and 73 is 12V or higher.

Cheers,
Robin

[Stewart]

I'm assuming you checked that the crank position sensor had the correct resistance.

Disconnect your battery, disconnect the ECU.

Reconnect battery.

Turn on the ignition (doesn't matter about immob).

With meter in voltage mode, measure voltage between pins 59 and 54. It should be 12V or higher.

Now using a length of wire connect pin 59 to 54 (be careful not to connect the wrong pins).

You should hear the clonk of the main relay inside the MFRU.

Now measure the voltage between pin 73 and 19. It should be 12V or higher.

Assuming that's correct then the main relay/MFRU is working fine.

Next turn the ignition off.

On the VVC the cam position sensor is a VR sensor much like the crank position sensor. Disconnect battery and measure resistance between pins 16 and 42. I guess it should be 1300 ohms give or take.

Finally check that the voltage between pins 80 and 73 is 12V or higher.

Cheers,
Robin

Robin

Thanks once again for taking the time to provide step by step remote diagnosis. I was so disappointed that the ECU didn't allow me to start the car, I was putting off undertaking the above checks. I have now done so and report the following:-

With meter in voltage mode, measure voltage between pins 59 and 54. It should be 12V or higher Reading 12+V

Now using a length of wire connect pin 59 to 54 (be careful not to connect the wrong pins).

You should hear the clonk of the main relay inside the MFRU. No clonk

Now measure the voltage between pin 73 and 19. It should be 12V or higher. Reading 12+V

Disconnect battery and measure resistance between pins 16 and 42. I guess it should be 1300 ohms give or take. Reading ~1230 ohms

Finally check that the voltage between pins 80 and 73 is 12V or higher. I can't get a reading, with ignition on or off

I am tentatively thinking most of this is good news and perhaps points towards a bust MFRU? Although should I have seen a reading between 80 & 73?

Please can you let me know what your diagnosis is. I do so hope it is *just* the MFRU. Every time I go near the engine bay now I am shaking for fear of doing more damage!

Thanks again for your help.

Cheers

Stewart

[robin]

LOL. I did say to take it to MMC and get them to sort it ... would have been less stressful and probably not much more expensive

Anyway, No clonk from the MFRU doesn't tally with 73/19 reading 12V. 19 is the main feed from MFRU to the ECU and it should not be live unless the 59/54 link is made and causes a clonk. I would be inclined to go back and measure 73/19 with the 59/54 link out and see if it's 0V. Then put the link in and see if it comes back to 12. If it does the MFRU main relay is working even if you cannot hear it.

Re: pin 80 not being live. Check fuse 8 (7.5A) so-called battery services fuse.

I should have got you to check pin 61/73 with ignition on and off. It should be 0v off and +12 on. If it's not then check fuse 7 (10A) so-called ignition services fuse.

Cheers,
Robin

[tut]

As Robin suggests, if you are not getting any further with the problem Stewart, speak to Craig, he will sort it out.

tut

[robin]

I'm happy to help remotely for as long as it takes, but if you need it done quickly, Tut is right.

Cheers
Robin

[Stewart]

Thanks again Robin. I will re-check tomorrow night. I've now had half a bottle of red so don't want to muck about with it.

Are the fuses you mentioned the ones next to the ECU? I did check these before, but will check again.

I initially spoke to Craig but understandably he didn't want the car until they had a new ECU which wont be until 21st December. I believe the cost was also in the region of £600 for the new unit

Anyway, No clonk from the MFRU doesn't tally with 73/19 reading 12V. 19 is the main feed from MFRU to the ECU and it should not be live unless the 59/54 link is made and causes a clonk. I would be inclined to go back and measure 73/19 with the 59/54 link out and see if it's 0V. Then put the link in and see if it comes back to 12. If it does the MFRU main relay is working even if you cannot hear it

I actually misinterpreted your initial instructions and did just that. 0V when 59/54 not shorted and 12+ when shorted and ignition on.

EDIT: I have just checked and I see fuse 8 is in the fusebox at the front of the car. I did initially go to check these but as the car has had an alloy rad put in it, I couldn't get the fusebox cover off I'll check 7 while I am in there.

Could these fuses now be all that is preventing the car from starting? I take it there is no point buying a replacement MFRU then?

I do feel like "we" are getting close.

[Stewart]

Robin

As usual you were absolutely spot on. I admit to not having checked the fuses in the front previously as I couldn't get the splash cover off the fuse box as one of the screws is obstructed by the pro-alloy rad. With a bit more determination I managed to get it off and right enough, fuse 8 was blown. I checked all others whilst in there and they were fine.

I plugged the ECU back in and reconnected the battery. The car then fired up immediately and seems to be running absolutely fine. I wasn't in a position to drive it, so I let it come up to temperature. I then gave it a quick press of the throttle up to 6k and the VVC appears to be working fine also.

I now just need to re-attach the MFRU to the chassis and put the ECU splash cover back on. Any tips on how to do this? It is so tight against the throttle body where the butterfly/cable mech is. I am also keen to give the car a wee run just to make sure all is in order.

Thanks again for taking the time to post. I know that it easy to just skim past, but by taking the time to painstakingly post the processes involved you have truly lifted a weight of my mind and saved me a lot of cash. I definitely owe you a beer or 12!

Antoine still seems keen, but understandably both him and I are now getting a little concerned about arranging flights etc in case the weather is crap. He is also getting busy at work and will find it difficult to come for the car before Christmas now - we will see. It wont be the worst thing in the world if I hang onto it. I have kind of become attached to it now that it is working again!

Thanks again for everyone who helped and for the messages of encouragement received.

Delighted!

[simon]