recently, i let my friend borrow my 4runner for several months so he could have something to drive. the first day i got it back, several things happened (confirmed my gut feelings that i should not let it be borrowed). i was driving up a steep grade in 3rd, rpms about 4000 or so and the exhaust got exponentially louder. i thought exhaust leak, no problem. i drove to work with it pretty loud and checked underneath to find the O2 sensor just about blown out of the exhaust pipe. later that day, my boss asked me to drive him to the store to get a drink and on the way back the engine cuts off while driving. crap, what now. i checked the fuses and the ECU fuse is blown. i replaced and it starts up but dies within a second or so with the ECU fuse blown again. i checked the O2 sensor and now it is completely out of the pipe and hanging against the exhaust, wires probably burnt a bit but still attached.

Will this cause the ECU fuse to blow?
How do I fix?

the vechile has headers and a Y pipe that funnenls down to a smaller dimention. After the Y pipe is a 5" piece that is welded that housed the O2 sensor, but that piece is completly rusted from the weld back to right where the muffler is welded. I had a exhaust place look at it and they looked baffled as to how to fix it. I would like to be able to start it, and drive it to another shop to look at it but do not want to have to tow it there. The hole where the O2 sensor is probably a little larger than a half dollar. Thanks for any advice.

Sid Crocker

Common cause is that the O2 sensor wire insulation was melted with the exhaust manifold contact and that caused the inner wire to short to the braided shield. That short can cause the EFI fuse to blow. You could test for continuity at the O2 connector and see if any of the wires are shorted to each other.

+1 this pops the EFI fuse instantly i troubleshooted for 4 hours and then found it pulled the stuck wire off the exhaust and started right up...this was after a $400 4WD recovery tow