ECU

[Elizabeth Law-Bartle]

I have a 51 reg yaris, had it from brand new, broke down for the first time last Sunday! Been told it might be the ECU. Might be expensive to fix. It's had a good run at 20 years old. Anyone else have any knowledge or experience of this happening? 

[Gerg]

What are the symptoms of the breakdown, for example, any unusual lights on the dashboard?  Does the engine still turn over on the key?  Was the engine running well just before the breakdown occurred?

Also, were there any other strange happenings in the days and weeks leading up to the breakdown?

Do you still have both ignition keys, by the way?

[MRichards]

If the ECU does need replacing, you might be able to keep the costs down by buying a used ECU from somewhere like eBay for £30-50 (based on a quick search I've just done). You should research whether your locks will be replacing/matching to that specific ECU, I'm not sure whether this is required for a mk1 Yaris (someone on here will likely know the process better than I do).

[Elizabeth Law-Bartle]

7 hours ago, Gerg said:

What are the symptoms of the breakdown, for example, any unusual lights on the dashboard?  Does the engine still turn over on the key?  Was the engine running well just before the breakdown occurred?

Also, were there any other strange happenings in the days and weeks leading up to the breakdown?

Do you still have both ignition keys, by the way?

So it just lost power all of a sudden as we were slowing down for rb and it stalled... And wouldn't start again. When turned key in ignition it would make the sound like it's about to start up but didn't. Aa couldn't fix it and that's what my mechanic has come back with it being - the ecu. It's getting sent off to see if can be fixed or not... 

- it was running perfectly fine before. No warning lights, nothing before it cut out. 

- I do have a spare key, do you think that would work?

 

Thanks

[Gerg]

The ignition keys have a small, self-powered chip (not related to the central door locking electronics at all).  Each chip (so each key) has a unique ID, and the car's ECU is configured to the chip ID.  After reading your second post, I don't think it is very likely that the key is at fault, but it is such an easy/cheap item to rule out that I thought it worth trying.  The chip's ID is read (wirelessly) by a small circuit  that lives right next to the ignition key lock, and is connected directly to the ECU, to verify its ID as being correct.

If an AA man has been involved then all the initial (sometimes fairly obvious) fault-finding, and more, can be taken as 'done'.  And I think your checking the ECU functionality is worth doing.

If a secondhand ECU is bought, then your existing key's IDs (immobiliser chip) can be matched to it.  It's a straightforward process with the correct (garage) computer equipment.  I believe that it can sometimes be done without the computer through an elaborate sequence of ignition key turning/door opening/pressing brake pedal several times etc.etc.  But I don't know that this  'DIY method' works with your model and age of Toyota.  And it is quite a long and critically-timed sequence of actions that is needed.

ECU failure is so rare, that it is difficult to build up a clear picture of how an ECU fails in normal use, if/when it does.

The AA man is likely the expert here, and can also call upon the AA 'database of faults' to check your symptoms against other AA call-outs.

I can't remember another Yaris being reported on this forum failing in the way yours has, perhaps others can?

Hope this helps.

[Saxmaniac]

If it's gone to a decent tester and rebuilder they can give you a definitive answer and a solid repair. One highly regarded one is ecutesting.com