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sprinkles08, ASE Certified Technician
Category: Car
Satisfied Customers: 22655
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Toyota RAV4 CV: My car is a 3rd month 2006 Rav 4CV. 2AZ engine.

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My car is a 3rd month 2006 Rav 4CV. 2AZ engine. Stupidly in the dark, trying to start the car with a flat battery I connected in reverse polarity. I have replaced the blown 120A ALT fuse, all other fuses appear to be OK. Motor cranks over, headlights, dome lights, indicators, horn, power windows and mirrors now work. Motor will not start, dash lights and radio will not work. What more can I do? Relay integration block does not have a 20A EFI MAIN fuse or a 10A HORN fuse. Both locations are capped off but below are 10A and 20A A/F fuses which appear OK. Would appreciate any help you can give.
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I see your question has been up for an extended time without a response. Do you still need help?

Customer: replied 4 years ago.

Yes I do, car still not turning over.


Unfortunately it sounds like you've probably damaged the engine control module at the least. There are many sensitive electronic modules on a modern vehicle and they aren't able to tolerate a battery or jump start being applied backward.

If all fuses are ok then the next step would be to connect a scan tool to verify the engine controller isn't able to communicate. If it's down then it's powers and grounds will need to be checked, and if they are ok then the module will need to be replaced. If all fuses are now ok then the powers and grounds are likely ok.
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