2008 Toyota Prius immobilizer ECU

Anyone have to replace an immobilizer ECU and then the engine wiring harness?

Car would not power on, dashboard was blank, but hazards, headlights, and dome lights worked. Seemed associated with rain events. Dealer could not reproduce problem, so we took it back until it would not start again. At that point the they said the immobilizer ECU needed replacing. They said car was fixed, but when I went to pick it up, the same problem still existed.

Now they say the engine wiring harness is the issue, as they located a problem between the P connector and the ID codebox. They say the ID codebox was showing 5 volts or lower when the small battery was fully charged at 12 volts. They say this indicated that the engine wiring harness has either a cracked wire or a corroded connector. When testing, they blew out the new immobilizer ECU they put in for $1,900. They said they are replacing the immobilizer ECU, but the engine wiring harness will need to be replaced at a cost of $3,956 which they claim is a discount from the $5,132 they wanted initially.

The car has never given us trouble before this situation. It is a 2008 that we bought new, and it has only 122, 000 miles.

Do we just junk this car or pay $6,000 to $7,000 total to bring it back?

I would never spend that much on a ten-year-old vehicle.

But that’s just me.


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Unless this is a flood vehicle, and was submerged in water, I can’t think of any reason why the wiring harness cannot be inspected and repaired in-place. I also can’t think of any reason why it should cost anywhere near $4,000 to replace. In fact, you could use that $4,000 to buy a used 2003-2006 Corolla with similar mileage, which would likely give many years of trouble-free service.

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