2002 Civic EX - ECU not communicating

Hey everyone,

I have a 2002 Honda Civic EX. One day I tried to start the car and while it was starting it wasn’t turning. I had it diagnosed twice saying the ECU was bad. I replaced the ECU (matched part #) with a used guaranteed good one, took it to the dealer to have it reflashed. They said that the ECU was not communicating with the computer, the green key light was not flashing on at all. I had someone else come look at it, and they said it might be the anti-theft mechanism on the steering wheel column, and also said they go bad all the time. I went to the dealer to get that part and they told me they almost never go bad. The conflicting information makes everything very confusing. I just need some direction on what to test. Also, I do have an aftermarket alarm (which I’m not sure how to disable or if it’s disabled) and an aftermarket radio (which I just disabled). I’m not sure if this is related but it might: my aftermarket radio has an aux port which has worked just fine when I installed it, but within the last 8 months or so, every device I’ve plugged into it has had its left audio signal shorted. I’ve had this happen to 4 different cellphones, I only mention because it might be another instance of the electricity doing something strange.

Grateful for any guidance on what I should do!

Clarify what you mean. You turned the key to “start”, then what happened? If something wasn’t turning with the key in “start” that you think should have been, what was it?

Sorry, I meant it’ll make the initial starting sound (cranking I think?) but won’t actually start. Thanks for replying!

Ok, so you turn the key to “start”, you hear that rrr rrr rrr sound, but it doesn’t catch and run. That’s called “cranks ok, but won’t start” in mechanics parlance. Provided the engine ran ok before, and this symptom suddenly appeared, and no other event (like overheating etc) occurred which might have damaged the engine’s internals, then the cause is usually either lack of spark or lack of fuel. Shops have simple tests for each. If you want to take this on as a diy’er task, post back and folks here will give you some ideas how to test for spark on your civic. An outlier would be a problem with the valve timing, such as a broken timing belt or timing chain. Do you know which of those your civic uses?

The after market alarm system prime suspect in my book, get it disabled if possible.

If it is the alarm system doing it, usually the shop will discover no-spark cause, as the alarm system mistakenly disables the ignition system.