Rep Power: 0

Driving home one night and the check engine light comes on notice immediately it's starting to sputter. drove it maybe another mile to have the codes read and it threw a code for a camshaft sensor. I replaced it the same night and the car was doing the same thing after 3500rpms, if I didnt let the car get to 3500 I could drive as fast as I wanted to. It did the same thing. I was told to replace the vtec solenoid. Replaced it and nothing changed. I had the codes read again, I was told it was the connections to the camshaft sensor and that night I replaced the pigtale leading to the sensor. I took the car for a test drive and it seemed fine (would get to about 5000rpms) then as I was coming back home on the freeway, the battery light came on (flashed) then the check engine light came on, the rpm and temp gauge both dropped to nothing and the car seems to die out and was able to get it home very slowly. I came out the next morning and tried to start it, it started but after a hard crank and idles rough. The key light is now flashing the check engine light is on and on the speedometer the car wont register D,D2,D3. The car will let me physically move the shifter but it wont show on the speedometer. I can drive it but gassing it, it moves really slowly and you can hear like a whirring noise. The car reverses faster than it drives. (Goes into reverse and neutral with no issues) I checked all fuses none were blown, I checked spark plugs, I've check all my ground wires, I've cleaned my battery terminals, the car has alot of miles but doesnt seem to be an engine or transmission issue. Seems to be electrical. Any help would be appreciated.

 
Rep Power: 0

Also tried connecting a code reader after all this happened but now will not read.

 
Rep Power: 225

Any work done recently? Usually when a scan tool will not connect to the PCM it's because the alternator mounting bolt is loose.

 
Rep Power: 0

Other than what I did no

 
Rep Power: 225

Check the alternator bolts, clean all ground cables on the engine and battery as well.

 
Rep Power: 0

Done. I cleaned the terminals and checked the ground wires that I could find. If the ecu was fried, then how is the car still starting?

 
Rep Power: 230

Since the gauges dropped while driving and the battery was dead, definitely check

-alternator tensioner
-mounting bolts
- alternator itself

Check to make sure that the ground connection to the head is secure and rust free.

.......

May need a new battery to, after it was drained so low.

Small chance the ecu was fried due to alternator being loose, causing unstable voltage/amperage. Test all of the above, if connection to diagnostic port persists to fail, the ecu may be fried.

 
Rep Power: 0

The battery didnt die the light just flashed. The car is still starting

 
Rep Power: 230

Flashing battery means that the charging system is failing to charge the battery while driving. Meaning instead of operating off of the alternator, while driving, the vehicle is consuming battery voltage.

Meaning the battery will be lower in charge than normal, if it deep cycles too low, you'll never be able to charge it to capacity.

 
Rep Power: 0

It hasn't flashed since that one time. Also the compressor I noticed isnt coming on

 
Rep Power: 120

When you said you “replaced the camshaft sensor, then later replaced the pigtail” did you or anyone else touch the alternator? If yes, that may be the problem.

Did you disconnect the battery before cutting the camshaft harness plug off and wiring a new plug on? If yes then that may be the problem.

Are you sure the electrical work you did is not shorting out?

Now if we rule all that out, it’s still very likely your alternator “lost” it’s electrical ground through the mounting bolts and back-fed through the PGM causing all these issue.

No instrumentation, transmission not working right, no communication, all fuses still good lends itself to either bad ground or bad PCM.

To be clear a burned out PCM can still function enough in backup mode to allow limited drive-ability, a non-grounded PCM usually won’t.

 
Rep Power: 0

If I wanted to replace my ecu myself how would I do it? What exactly would I need and what would I need to change?

 
Rep Power: 225

If you replace the PCM without first figuring out what caused the problem you're going to end up with a second damaged PCM. You need to check everything that's been mentioned before going any further.

 
Rep Power: 0

I had it diagnosed at brakemax and they said it was a lose alternator bolt. But I was quoted 2k to do the work and I dont even think the car is worth that much. So what are the parts I need to do this myself

 
Rep Power: 225

$2k to tighten an alternator bolt?!?

You don't need any parts unless a bolt is broken. Remove the alternator and clean the mounting points while you can. Reinstall and make triple sure all bolts are tight. Start the car and see if the issue goes away, if not you'll be in the market for another PCM.

 
Rep Power: 513

Holy crap. Find a new shop. If I ran a shop, that's something I'd do for free to take care of the customer. I'm pretty sure everyone here that's had a shop replace their head gasket has been quoted less for that than your alternator bolt.

 
Rep Power: 0

It was to run a test on the ecu to see if it was dead or not. I want to replace the alternator, the ecu and what else do I need to replace with the ecu? The keys? The ignition?

 
Rep Power: 0

Do I have to take the car somewhere to have it flashed or can I bring in a bare ecu and keys

 
Rep Power: 513

From what I'm to understand, you have to bring proof of ownership of the car as well as a bill of sale for the new ecu so the dealer can program keys. Something like that. Just to make sure you didn't steal the ECU kinda deal. I'd check with your local dealer to see what they say, but the above is what I've heard.

 
Rep Power: 0

I see alot of people selling the keys, ignition/immobilizer and the ecu as a matching set online, if I bought a set and installed them would I need anything flashed or would I be okay because they already match?

 
Rep Power: 225

If you bought a matching set then you would not have to go to the dealer, simply replace everything and it should fire right up.

I would still recommend tightening the alternator bolt and testing before just replacing everything. There's a chance nothing was damaged. Tightening a bolt costs you nothing but could save you hundreds.

 
Rep Power: 0

I did tighten it, it did the same thing so I'm gonna replace everything and see

 
Rep Power: 0

I wont have to worry about having it programmed to the mileage or anything? Is that stored on the speedometer?

 
Rep Power: 120

Important things, make sure the ECU is for 2004-2005 EX Automatic “ONLY” do not buy one that is vague or implies it works with a wider range of cars.

Technically the ECU also stores mileage, but that’s Factory precaution against people just swapping out / disconnecting instrument clusters for warranty reasons.

Your mileage indicator will not change.

 
Rep Power: 0

I need one that is a plr-p72, does the bottom serial number have to be exact or is that the ecus personal number? I have yet to see two that match so I would assume as long as the top numbers match, the ecu came out of a 04 honda civic ex AT 1.7l then I should be fine

 
Rep Power: 120

Sounds like that should work just fine.

Consider ordering a new set of the breakaway lockscrews for the ignition.

It’s while it’s a real pain to remove them, it’s much bigger pain to try to reinstall used ones correctly.