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Hi Guys, i hope everyone is doing great on this forum...

Let me explain the situation that i'm actually dealing right now, About 2 months ago my beloved 7th Gen Automatic Trans '04 Civic EX started to have transmission problems, I was driving one day and it suddenly gear slipped to Neutral while i was going uphill, I managed to move the car by shutting thee engine off for about some minutes and started driving again, however after driving for about 5 minutes transmission slipped off again, so i was able to get home shutting engine off, driving for 5 mins, then shutting it back off and so on... I checked the CEL and it throwed a "Incorrect Gear Ratio" Error code, which I honestly don't remember the exact code, maybe P0730, I recall. So I took it to a Mechanic which changed Tranny Oil using Honda ATF Fluid but car was still behaving erratically, Took it to another mechanic that said I would either swap the Tranny for a used one, or try to rebuilt it, problem is, Where I live there are shortages of spare parts for Honda Transmissions, so at the end I decided to swap it for a used one, when the swap has been made the mechanic stated that he tried two different transmissions and both of them gave the issue of Blinking D Light on Dashboard and that he tried different solenoids and the issue still persisted, he mentioned it should be an electrical failure. I took the car, that now at least is able to move, however only moved on "Manual Mode" First Using D2, then increasing to D3 and D once it gained momentum, at this time the D light was blinking since the car was started and will stop blinking if I shut the engine off. CEL was on and gave P0974 and P0977 Error code alongside a weird C3409 Chassis Code that I couldn't find an explanation for but that one cleared itself on a couple of days.

While I was at home I Noticed that there was a small wire that wasn't plugged in that goes to the A&B Solenoid on the Trans so I Plugged in back, however D Light was still blinking So I supposed that wasn't the issue, a day passed and I was again at my garage looking for some other things when i checked the fuse box, (Since i previously was working on the AC System before the Tranny issue) And i realized something, there was a 80 Amp Fuse that was missing, according to the fuse box sticker it belongs to something called "EPS", I did a passthrough bridge using a small cable I found lying around to see if that was something useful to the car's issue, when bridged it caused a little spark, meaning that there was supposed to be a fuse there, but since I honestly don't recall if that fuse was indeed there before taking the car to a mechanic and the fact that I didn't know what the EPS was for i decided to leave it like that...

To my surprise when I got in the car that same night I noticed that the D Light was not blinking at all, and that the car was shifting like it should, "Beautiful..." I thought since car was fine and without an issue for the rest of the day, but little did i know that the problem will re appear, this time if shutting engine off and starting it again it will stop blinking before blinking D re appears after about 5 minutes of driving this time only giving DTC P0974... but then...

I started hearing a grinding noise whenever the AC Fan comes on, from near the Steering pump is, so I thought, maybe the grinding noise comes from the fan since the car was parked for about a month or two and needed some type of lubricant to correct itself, but then I notices something weird;


If I have the engine On, but parked the car will make the AC and Radiator Fan to be On, and it will start making that grinding noise again, seconds after the grinding noise appears the D Light starts blinking again... So I popped the hood up, and started smelling like burnt charcoal, I immediately noticed some smoke coming from where the alternator is, so I'm starting to think that the alternator has something to do with the Blinking Light issue, as i read on this forum that someone had fried up a PCM due to a loose Alternator... Would this be the case?

Current Code that I have gotten since Mechanic gave my car back:
P0974 - Powertrain
P0977 - Powertrain
C3409 - Chassis
P0730 - Incorrect Gear Ratio
P0420 - Catalyst System Efficiency below Threshold (Bank 1)
P0302 - Cylinder 2 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P0300 - Random/Multiple Cylinder Misfire Detected

At this specific moment, the only ones I'm getting are:
P0974 - Powertrain
P0420 - Catalyst System Efficiency below Threshold (Bank 1)


Thanks for the long read fellas!

Edit: I found a little more info on that C3409 Code, but it applies to Toyota vehicle, i Honestly don't know if it works or be valid for my Honda...

 
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Alrighty, So i come with an update on my issue, It turns out that the sound and smell was actually coming from a bad A/C Pump, looks like the clutch got stuck and the A/C pump was always running, the issue is that I believe I had a leak so it made the Pump go bad thus causing the screeching noise and the bad odor like something burnt, thing is that the belt that goes to the Motor-Alternator-Pump snapped and i had to replace it, this time Bypassing the A/C System using a different type of belt (In case you need belt sizes to bypass A/C System, instead of using the 6PK990 which is the recommended one for LX & EX Trims, use the DX belt which is 6PK850 which is the model that doesn't have A/C System)...

Anyways, I found the culprit of my Blinking D or D4 Light, and it was so stupidly easy to repair... Turns out that when the mechanic did the transmission Swap, he broke the Connector of the Shift Solenoids on the Transmission, so when plugged the connector was loose and making the D Light Blink giving the error codes P0974 & P0977, so all I did was by passing the connectors and plug them directly using shrink isolation tape and soldering... Car now runs as smooth as new!

Now I just need to focus on get the A/C System working again! And I also couldn't confirm why the C3409 Code was also there, but it disappeared after a couple of days cannot say it was related to the issue though.

I'm a little bit sad cause I wasn't able to get replies to my post, but hopefully someone else might have the same exact issue and found my reply useful!

 
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thanks for coming back with causes and solutions.
Majority never tells u what worked for them...