2005 Honda Civic ECU

That is the part number, not a code. Yes, the part number should match.

There’s a relay used on some Honda’s (Civic is one of them) that is a notorious cause of no-starts, stalls, etc. As I recall the models most affected were late 90’s, maybe into the early 2000’s. Suggest to search the forums here for posts about that relay, search link upper right this page.

One problem w/this theory, when that relay fails , by reports here anyway, it usually fails hard … i.e. it stays failed, and the car will never start until the relay is replaced. The forum search will likely tell you if that’s the only failure mode.

Have you done this yet?

George is talking about the PGM/FI relay.

And they can fail intermittently depending on the ambient temperature.


For my Miata, I found a service on eBay that repaired and re-programmed my ECU for about $120. I presume that if they found that it did not need a repair, that they would have notified me.

Update: Took the car to the dealer. They replaced and are confident it was the TDC sensor. Time will tell. Thanks for all the opinions.

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What is a TDC sensor?

TDC – Top dead center - It has to do with controlling spark to proper plugs as near as can put it .

The real mechanics that post here will explain it better .

Yeah, I just never heard of a ‘TDC sensor’. Looked it up, another name is cam position sensor.

I’d think a TDC sensor would be for the crankshaft rather than the camshaft. Guess that is what happens when I do my own thinking … lol …

I wouldn’t have guessed a failed camshaft position sensor would prevent the engine from starting. That’s used to ID if it is the intake or exhaust stroke. If it fails, the computer will often just fire the spark plugs on each stroke. Guess whether that method is used, depends on the design.

I’m a bit hesitant to go along with that diagnosis. Hopefully it is fixed due to a proper diagnosis and this is all not a guess of some sort.
The thought keeps coming to mind of a faulty ignition switch since that has been a common problem for decades and even involved a Recall on Hondas prior to 2005. Just because a vehicle is not covered by a Recall it does not mean they do not suffer the same issues and I seem to remember a fuel pump corrosion Recall also.

One might hope those possibilities would have been considered.