martinsmartin

Hello Folks,

I never needed to post anything on this forum before until now.
So I just registered in hopes that someone can help me out with some questions that I am assuming is simple to answer. Technical details are below my questions.
There's a lot of ECM questions for the 7th gen civics but its almost too much as I can't find an absolute answer. Google wasn't my friend tonight either.

Here are my questions:

1- If I bring a couple of ECMs to the dealership to get flashed for my VIN/key. Shouldn't they be swappable so to speak? The dealership told me they programmed 2 of the ECMs and they are getting cylinder 3 misfires with both... But yet, I tried to use these new fangled flashed ECMs but the car doesn't start. It only cranks and the green key shows up on the dash. Shouldn't I just be able to use any of them now since they are synced with my VIN/Key? It only starts with the original ECM. ( I should've kept the original with me... Lesson Learnt )

Would they "unflash" them afterwards just to be jerks? I need to know what are my remaining options because it will be the scrap yard next unless I can get some sort of semi/fully functioning ECM to continue my adventure. So frustrating...

2- My orignal part number for my ECM is 37820-PLM-C53. The spare ones I got from the scrap yard are 37820-PLM-C52. The C52 should be compatible for a reflash right? I got them from the same type of civic ( 2001 LX AT ) All plugs/pins match up.

Thank you for reading and any help is appreciated!

Cheers!
--

Technical info for the need to know people!

I finally nailed down an issue with a vehicle I am working on. There are no pulses going from the ECM to injector number 4. ( Noid light doesn't respond ) The injector ground was tested good, the positive lead of the injector tests good and has continuity to the ECM. (using test light ) Positive also has no resistance through and through.

Just some FYIs
All 4 coils are producing spark ( visual )
All 4 Coils were tested/swapped on another vehicle with success.
All 4 Spark plugs were changed.
All 4 Injectors were changed.
Fuel Pressure shoots out the Fuel Rail with ease.
Vaccum was not tested.
Getting random misfire code from the code reader and a p0304 misfire cylinder 4.
Cylinder 4 never worked since this incident started. Still doesn't after today.
The solder trace for the Injector 4 Pin ( Yellow/Gray ) is discoloured compared to the other ECMs I procured. ( Internal Motherboard )
Compression test results ( 5 cranks/Dry only 1 to 4) 180 178 180 181

The reason I think the ECM crapped out is because of extremely shitty grounds. They were barely any strands left. One was disintegrated completely.

ezone

Honestly, I have not tried to work with a situation like that (multiple PCMs).

I know the key, the immobilizer control unit, and the PCM all have to be married in order to start the engine.

Right now I see no reason for correctly programmed PCMs to not work. I think the immobilizer can be written to multiple PCMs....as evidenced by your original PCM still starting the car.

Maybe, but that would take extra time to do.
SOME people might be dickish like that though.

Talk to the service manager, see if he might make them redo it?
Neither number shows up in my USA parts catalog.
Are you in Canada?
On a purely technical note here, this did not make sense to me.


The 4 injectors are supplied with 12v+ from main relay #1 on the yellow/black wires. There is a splice pack in this circuit.

The PCM pulses ground to operate the injectors (brn, red, blu, yel wires).





I'm thinking a circuit that has high resistance or a weak connection can appear perfect during a resistance or a voltage test but fail completely when loaded (amperage).


You say #4 won't flash the noid light..... you need to break this down one wire at a time to see which side is failing..... The hot side, or the pulsed ground side.

I'd test these with the engine running and injector connected, backprobe the injector connector to measure 12v (or use a test light) and then see if it will pulse the light manually connected only on the ground side. (did that make sense?)

If it's missing the hot, then I'd go to the splice packs on top of the valve cover and test there. (The cube between coils 3 and 4 contains the yellow/blacks.)
If it's missing the pulsed ground I'd go recheck that right at the PCM connector B2 yellow wire (for injector #4) next.




I hope this was not a terminology issue at the dealer.
Programming is what we usually call doing the immobilizer keys. (key programming)
Reflash is usually a software update.

How did they manage to get this if your problem is #4?

martinsmartin

Thanks for replying! I really appreciate it.

Yes I am Canadian.

I guess I had misunderstanding on the injector wiring... When I get the chance today, I will test this.

I wasn't sure at first but I went and did a preliminary controlled test on another functioning vehicle with functional pulse. - I hooked the test light to battery negative and probed the constant 12V. I hooked the test light to positive terminal and probed the pulse. I will head back to the dealership to test these as advised.

But before doing all that... I want to have an ECM that's not immobilized with my key. I will demand it! I will talk to the service manager.

Just so I am on the same page here... A software update wouldn't be needed right? To my understand, it's just an immobilizer issue ( green key on dash ) I just told them I want these ECM to work with my car and they don't. Once the car starts with a separate ECM then I will go forward with parking lot testing!

I really don't know how they got misfire only on cylinder 3. They close at 5PM so I didn't have a chance to interact with them. Maybe I'm just clueless, we'll see.

Cheers

ezone

Sounds correct
Right, in theory LOL

Correct

Good chance the advisor isn't repeating stuff accurately. That happens a lot when they don't have deep technical knowledge or care about the little details.

martinsmartin

Alright! Sorry for the late reply.

After explaining slowly to the dealership what I wanted, they reprogrammed a scrap yard ecu with the old key like I wanted for free. This fixed the cylinder 4 issue! I opened the old ecu and traced the pins on the motherboard and you could see a slight discoloration on the chip where the injector 4 pin connected to.

After following your instructions and testing pulses/12V connections to the injectors. I could see that electrical was working properly for all injectors. I retested sparks and coils also. But we were getting cylinder 3 misfires from now on!?

The technicians worried me and almost convinced me that this engine was pooched and that their might be a valve problem or timing issue. I almost gave up on this guy... This car was 5 hours drive from my home and I didn't have access to all my tools. I was getting fed up of this project. It's been out of commissions since May and I've been travelling back and forth to get this going.

Anyways, I drove it back to the place where I was working on it originally ( 3 miles away ) on 3 cylinders.

I did one last check and I had a sneaking suspicion that one of the refurb injectors I installed failed at one point throughout this escapade... So i took injector 3 and put in cylinder 1 and vice versa for injector 1. Low and behold I had a cylinder 1 misfire... My fault for being too cheap on the injectors... I replaced it and the rust bucket is alive again! No CELs drove it for a couple hours after doing 2 oil changes ( engine oil flush ). 100% brand new!!!! Right!?

Thanks for your help ezone! It cleared up some misdiagnosing on my part.
Now I will go back into hiding in my own little world.

Cheers

ezone

Good to hear it's turned out well!

Kinda surprised at the injector driver failure, I wonder if an injector had internally shorted its winding or something.