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jimbo34
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Discussion Starter #1 (Edited)
I need some advice please. I was trying to jump start my wifes 2003 Mk1 Yaris in the dark and somehow :frown: managed to reverse the polarity on the jump cables. The car was completely dead afterwards with the 120A ALT (alternator?) fuse and the 15A EFI (fuel pump?) fuses which were obviously blown.

After trying to jump again (correctly this time) the car had power but when I turned the ignition, the engine would turn over (starter working) but the car won't start.

I've taken the car to a local garage, the guy changed some more fuses quickly but says because the engine check light doesn't come on when the key is turned, the ECU is broken. I'm inclined to agree but for one thing, the immobiliser switches off when the key is inserted (red security light stops flashing). Does this indicate that the ECU is still, at least partially functional or are the 2 unrelated? Could it not be starting due to problems with the alternator or fuel pumps?

Finally, if it is the ECU, I've seen second hand units on ebay for less than 100 euros. Is it a straightforward job to simply plug in a new one and change the ignition switch?

Any help would be appreciated!
 

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I would look at the part number on the ECU and look that up to see if it fits other model years. Generally speaking, you need the same model year and transmission type unless a particular model run went completely unchanged through each year, and even then small changes could have been made (idle speed, etc.). But I would get your part number off ECU and verify what years compatible with, and go from there. Even then, I would still want the donor ecu for the same type transmission that I'm putting it into.



*I'm not sure, but you might have to get it get it flashed as well. Not sure about that.
 

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jimbo34
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Discussion Starter #3
thanks for responding! I really appreciate it.

In the end I've fixed it by changing the EFI No.2 fuse located on the instrument panel junction block. This fuse is slightly hidden by the steering column and is located on its own away from the other fuses on the side of the junction box.

After doing this, when I turned the ignition key the check engine light came on and the car jump started normally.

I guess on these cars if the immobiliser is switching off when you insert the key, then its worth looking at other more simple electrical problems rather than just (expensively) replacing the ECU.
 
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