1991 Acura Integra LS B18A1; Automatic Transmission (161k miles)
Today my 10 amp ECU fuse located under the hood in the main fuse box blew. The car started right up and drove great to my destination, sat for about two hours, and then was cranking and not starting and flashing the S3 light and displaying a solid CEL. This happened once before under similar circumstances back in February of this year and so I immediately went to check the main fuse and box and sure enough saw the 10 amp ECU fuse was blown. I popped in a new one and drove home with no issues. In retrospect, I should’ve taken my time and read the CEL code before plugging the new fuse in to maybe get some clues and will be sure to do so next time this happens.
It’s unclear when the fuse blows exactly, whether that’s when turning the engine of or on. Other threads I’ve read seem to suggest it can happen when turning to accessory, but I can’t replicate that. Those threads also seem to have it happen every single time, whereas this was the second time for me after almost three months had passed. I don’t think its happening while driving because I am pretty sure the car would just shut off.
Currently I am in the process of researching what might be causing this occasional overload on the ECU and trying to study the wiring diagrams to get some clues. Appreciate any tips or suggestions!
Are you battery posts OK? Whenever I get weird electrical stuff I check that first. My next thought is a poor ground in that circuit.
What was the temperature like outside?
I have the electrical wiring manual too. I can review those pages that align with that fuse.
Battery posts should be okay, but I’ll double check them for any crud on the terminals. Temperature was ~80F, I was parked in the sun. Let me know what page you’re looking at in the wiring manual because I am struggling to find a diagram in it with that specific 10 amp fuse labeled.
Going for a drive today and will see if it happens again. Did some testing last night and I wasn’t able to replicate the blow when I turn the key to accessory.
Adding some pictures for clarity’s sake:
Fuse that’s blowing is the 10A ECU fuse in the top left of this main fuse box under the hood.
Positive terminal was a bit crudded up, cleaned it off and looked okay otherwise.
I’ve had weird electrical stuff happen when my positive terminal went bad. That’s why it’s my go-to to check first. I’d suggest changing it out altogether too.
Yeah I’ll be able to check the wiring diagram on Thursday.
Any updates to help hone down the issue?
Thanks for following up. Car has been running fine since I changed out the fuse. Been keeping an eye on it to see when it blows, but hasn’t done it again yet. Was driving in similar circumstances today again with same weather, parked in the sun, and it started up fine with no hangups. Hoping to figure out what components are linked to that 10 amp ECU fuse to check those connections and see if wires are pinched or grounding out anywhere.
New symptoms have been appearing in the form of a noticeable loss of power in acceleration and top speed. Might be in limp mode? Seems like I can barely push it to get up to 60mph, almost feels like one of the cylinders might be misfiring or not firing at all. No check engine light. Reading other threads people suggest the fuel filter could be clogged up and so fuel delivery is being impacted.
Not sure if any of this is related at all to the fuse blowing but that’s whats been going on as of late. I have plans to replace the valve cover gasket this weekend and the cam seal plug to hopefully patch some leaks and will be on the lookout for anything obvious that could be causing trouble.
That loss of power could be plug wires, ignitor, or ignition coil too. Sounds unrelated to that ECU fuse though.
