Car was running, I shut it off and two mins later went to start back up and it wouldn't start. I was fixing the trans cooler line on the rad when the car was off and went to start the car to check to make sure it wasn't leaking and that's when I found it wouldn't start. The ECU fuse keeps blowing every time I put the car in the accessory position. I checked the o2 sensor wires and even unplugged it and it still blows the fuse. Checked the ground on the thermostat and opened the ECU to make sure its not burnt up. If I unplug the main relay then the fuse does not blow. So does that mean its the main relay or something else? Don't know where to go from here. Doesn't make sense to me since I didn't touch anything wiring wise when I was playing with the trans cooler lines (obviously I did something lol). I hate wiring problems, please help!

 

What kind of car is it? Start by unplugging ALL sensors on the engine, don't forget about the cam and crank sensors. I had this exact problem on my 05 Civic and it ended up being a shorted out crank sensor, Good luck, I am sure you will get it figured out.

 

Its a 94 Integra. There is no crank sensor cause its OBD1. I didnt touch any other sensors and the car was running before I touched the trans line so I dont get it

 

Still unplug all sensors and retry and report back.

 

Just because you unplugged the O2 sensor plug and it blew the fuse, the wiring can still be bad/knicked/exposed. Is the O2 sensor up against the firewall or other metal?

 

True.

 

No the o2 sensor is far away from everything and no wires exposed. Unless its the actual wires that go into the main harness?

 

Alright think I made a bit of progress chasing this down. I started backtracking and checking things that I already checked. When I disconnect the thermostat ground and turn the ignition on the fuse does not blow. So where does this leave me?

 

Interesting. I will see if I can find a wiring diagram and go from there, Do you know which sensors that ground is for? Like I said though, a short in any sensor can also cause this, A trick I use is I put a small light bulb in the fuse socket with a fuse in line for safety and watch for the light to go out, indicating that the short is gone instead of using 500 fuses. Good luck man, this sort of thing can be very frustrating, but when you get it figured out, the feeling is very satisfying

 

Good idea with the light bulb lol, Ive already killed like 15 fuses. I have no idea what that ground its for, I looked at one diagram and it appeared to be a lot of **** that ground there. I just finished pulling the whole wiring harness off the back of the motor so Im going to try and track it down from here. I also unplugged the pcm, injectors, alternator, iacv, map, tps at different times and tried it and the fuse still went. So yeah I love wiring

 

How do i make a fuse with a light bulb exactly?

 

I made the tool years ago, and it is very nice to have. It is as simple as getting a low wattage bulb and a socket. I grabbed an incandescent brake light bulb and socket out of a car at a junkyard and cut the wires to the plug so I had a complete bulb/socket assembly with 2 wires sticking out of it. You just insert the ends of the wires into the fuse socket and turn the key on. The resistance of the light bulb will not allow enough current to flow to cause damage. The light will light up brightly if there is a short and when the short is gone the light will significantly dim or go out. That is how I do it, it works great. Good luck