3SZ WON'T START, IMMOB?

Hey guys, it’s me again. To start with some good news: the 3SZ is in, and it all looks good in terms all the bolts, nuts, wires, plugs, hoses etc etc.

Now the bad news: the car will not run. The fuel pump runs, all the electrics work, the timing is right, and the starter works, but it won’t run. We checked for sparks: nothing. Everything else seems connected, so I assume that the ECU doesn’t give “the signal” for sparks. I think it’s because of the immobilizer. I used my own key, and the immob to which it’s paired. However , the ECU is different (because it’s from the 3SZ), and I think that’s the issue.


read “EFI ECU”

I think the fuel and ignition are cut off because of those codes. This is form the YRV manual, but I think the Sirion 2 ECU will work the same way.

People who did a K3 swap may say: “you can bypass the immob by switching the pin on the ECU”. The K3VE and K3VE2 have this option. However, this ECU doesn’t appear to have that kind of pin.



SIO2 is the pin that goes to the immob.

I’ve read this a few things about resetting the immob and registering a new key, but I don’t have a master key unfortunately.

But, maybe the immobilizer isn’t the problem, so all suggestions are welcome! I hope someone can help me find a way to make things work, because this appears to be the only thing that’s keeping me from driving this pocket rocket! @Mr_Gormsby @Mick perhaps?

(btw, if anyone needs anymore info, I have a lot of manuals etc so if you need it: please say so!)

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If you are using the cars keys and immobiliser but a different ECU the ECU won’t recognise the code for the key because it doesn’t match the code stored in the ECU.
Don’t think you need a master key, just need any key that previously worked with the car.
It may be possible to reprogram the ECU but you will might need a good scan tool.
Check out: Getting your toyota to run with a used or new pcm. Vin rewrite with autel scanner. Immobilizer reset - YouTube its refers to Toyotas but since they are related it might point you in the right direction.

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I tried that jumping the pins like stated in that video when I tried to get a Storia ECU to work in my sirion. Didn’t work unfortunately. I was told by a Toyota service place that you need a the scan tool Daihatsu used to reset the ECU code. There were 2, one was the Denso DS21 and I don’t remember the other, but is was Danso too. And you need the Daihatsu chip/cartridge. The Toyota service guy said that is how their repair manual stated the process was to replace a damaged or malfunctioning ECU.
EDIT: Other scan tool was the Denso DS-II. There seems to be one for sale here Diagnostic tool daihatsu DS II Original AS NEW | eBay
DOUBLE EDIT: It has to be the master key. The master keys were black plastic, while the copies were grey.

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I would suspect your problem is the immobiliser. Sorry but nothing else to add from DaryLW or b_hoves. All the best with it.

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Agree its most likely the immobiliser.
We had the same problem when fitting the EJ-DE into the Mira and the easiest way to solve the problem was an aftermarket ECU

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There is a small 6 pin IC in the ecu that stores the immobilizer codes.
you should theoretically be able to swap it out, there are plenty of how to guides on the net about how to do it on denso/Toyota ecus.
I’m pretty sure I have even created a topic about it here in the forums with a bunch of links and info

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Found it

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Thanks for the effort! I might be able to get the original key from the 3SZ, which would solve the problem, but I’ll definitely keep this as an option. Thanks a lot man!

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