Had jumper cable backwards when jumped car

BEACH0987

MEMBER
2005 SCION XB
1.4L
4 CYL
2WD
AUTOMATIC
177,000 MILES

I replaced the battery and 120 alternator fuse link. Car does not crank, but I hear a quick double knock click sound. Plus my 15 am2 fuse is blown and when I went to replace it with a new 1 with the car off no key in ignition it blew the new 1 also. I have ordered a new starter relay fuse and hoping that fix it. Any idea whats going on?

Saturday, March 14th, 2020 AT 9:00 PM

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Clearly the fuse blowing is the first priority. We need to check this circuit for a short to power. You may be correct that the starter is the issue but if you look at the wiring diagram at what else is on that circuit, we need to find what is drawing too much current.

Do you have a scan tool to check for codes? Then we need to see if you can communicate with the ECM. If you can't communicate with it then you have damaged the diodes inside on the circuit board. Basically when you reverse the polarity and send current backwards there are no circuit protectors on the ground side so the ECM gets whatever current is going through the circuit. It will normally blow the main engine fuse when it gets to it if it doesn't damage the ECM first. However, most ECMs are made to handle reverse polarity.

Let me know what you find.

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