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I drive an 05 civic lx. Just a few days ago. I was driving and the car shut off. Not completely though. I can start it, runs, and even revs up. But, my rpm sensor doesnt work, it runs really rich on start up and when pushing on the pedal the engine tends to sputter and stutter a bit and doesnt reach its limit (about 4k RPM). I tried 2 separate odm-ll code readers and neither were able to connect. I disconnected the battery for a few hours to try to reset the codes but I still get an engine light. As well as my green key flashes even while the car is running. At first I was thinking it could just be tps but after further digging and reading I'm thinking it could be my ECU? I checked the fuses and relays already and all are good. Just kind of hoping to get some other possibilities and maybe support on my thinking. Thanks in advance.

 
Rep Power: 223

Any work done on the engine recently?

Usually when we see these symptoms it's due to a loose alternator. There is a mounting bolt on the bottom of the alternator that is used for the ground. It is hidden and missed fairly often. Here's a few other threads with a similar issues.

https://www.civicforums.com/forums/3...need-help.html
https://www.civicforums.com/forums/3...-not-link.html

 
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Pulled off my power steering reservoir to look at the alternator which is new. Bolts had come loose so I tightened everything. Had battery disconnected to reset codes but to no avail. Green key still flashes and check engine light is on. Auto trans shifts hard into drive, reverse, etc. As well as all previous issues still. Any other advise?

 
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UPDATE: went ahead and pulled the ecm and inspect it. Nothing is wrong. No missing or pushed pins, nothing fried on the inside. I double checked the alternator(which is new) and it's now fine.

 
Rep Power: 223

The damage may have already been done. If your positive the top and bottom mounting bolts are tight you may want to start looking for a replacement PCM. Below the alternator there is one bolt going through the bracket and into the alternator, and another bolt going through the same bracket into the engine block. Both those need to be tight and the mounting surfaces sound be clean. Take some sand paper and scuff the mating surfaces up a little.

 
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I made my own post about problems somewhat similar to this, and now after reading your reply here that might just be a possibility for me. I was neglectful when installing a new alternator and didn't get my top bolt in all the way. Could this have broken my PCM?

 
Rep Power: 223

Replied in your thread.

 
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So the car has been sitting for about a month now and I still cant figure it out. Called a buddy of mine who has a better code reader made by snap on and it couldnt communicate with my ecm. But I can start the car and run it. It doesnt drive though and the rpm's dont read on the tachometer.
hebsaysbit might be a wiring issue but before I spend endless hours trying to find a short in a wire I would like to know any other opinions.

 
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Your civic might be in limp mode, does the rpm gauge jump when you start the engine? Or do you hear a lot of clicking noises?

 
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No. Rpm gauge doesnt move the slightest

 
Rep Power: 221

Ecu is fried because the alternator lost its ground (loose/stripped bolts) fairly common problem. Fix the alternator mounting before you get another ecu or you'll just fry the new ecu

 
Rep Power: 118

What stage of ECU death denial would this be?

Integrated circuits easily “die” without any external appearances of frying.

Grab a used ECU, bypass the fuel pump relay, and see if the car starts right up and drives normally. (Except the green key flashing).

And be sure all 4 bolts(including the wingnut) for the alternator are tight!