Prelude_5g00

I made a thread last week about my f20b swap in my 5th gen prelude. I used my old 5 speed tranny and ecu with the swap. For assurance, I had a licensed, specialized Honda/Acura mechanic do the swap. He knows his stuff and he's a really good mechanic, but after this swap while im driving, my check engine light will flash for several seconds, then stay on. If I accelerate, it will also sometimes start flashing.

I've heard flashing check engine lights can be serious, but can this because caused by a JDM engine being swapped into a USDM ecu? I'm worried that it could possibly be causing damage, any answers would be greatly appreciated.

Kronn 98SH

https://honda-tech.com/forums/honda-prelude-4/how-retrieve-cel-atts-abs-4ws-dtcs-2553408/#post38252637

Pull the code.

A Blue Lude

I'd guess you are running a JDM distributor with all 3 crank sensors (CKP/CYP/TDC) in the distributor. The USDM setup had only CYP in the dizzy and had CKP/TDC on the crank snout in order to meet OBD2 misfire detection requirements. However, you often need to swap oil pumps to mount the there, which is a pain

A USDM ECU will often throw false misfire codes in that case (flashing CEL = "misfire in progress that is causing converter damage") - check your CEL to make sure.

If that is your issue there are two solutions

a) Rip the whole timing side of the engine apart and the oil pan to install CKP/TDC sensors in the US OBD2 location
or
b) Run a JDM or OBD1 USDM ECU that expects all the sensors in the dizzy

Prelude_5g00

Hmm great, well option A is definitely much cheaper if I do it myself. I'll look into it. The car has absolutely no sings of engine misfire. It runs perfect, like brand new even. I'll check the codes tomorrow. But basically if I come back with no codes, the check engine light is faulty, and performance isn't affected?? If so I might just live with it for a while, and check the codes often to make sure nothing else has gone wrong. Again, thanks for the input guys.

A Blue Lude

No, the car isn't misfiring. IMO option B is much easier. I can't really say if there's a performance hit. I don't think so though. But I'm not sure if anyone's really tested it.

Prelude_5g00

I haven't noticed any performance hits but since I just got this engine, I guess I really don't know how it's supposed to perform yet haha. I'll see how it goes. The only reason for not doing option B is money. I bought this car for 4500 dollars thinking it was a good deal, and have spent about $3000 dollars in repairs as everything just began to break down. How convenient. Point is, I'm only a senior in high school and I'm broke. I still need headers, IM, etc. to make the power I want. One step after another I suppose...

Kronn 98SH

There is one performance hit. A JDM ECU will have a governor.

92civlude

This guy knows his stuff! I had the same ordeal. I ended up running a Phearble chipped OBD1 P28 ECU, conversion harness, OBD1 dizzy.

Daddydes07

i need help i have a auto jdm f20 and my d4 light flashes and when i come to a stop it jumps into first gear hard and the power steering humms im getting manufacture spped sensor code if i use e23 computer it doesnt flash but tranny dont shift right and motor has no power can anyone help what should i do besides go 5 speed (no cash left) i was wondering if i use h22 computer would that work but i looked at one on ebay and it had four slots but the third is empty mine is used pls help before im ready to start a bong fire lmao

Prelude_5g00

So I pulled my codes. I read a cylinder misfire on cylinders 1-4, as well as a random misfire code. As much as it makes me nervous, I really don't notice the cylinders misfiring. There are no symptoms whatsoever, besides the blinking check engine light.

92civlude

The ecu thinks there is a misfire because its reading a CKP signal from cam speed instead of crank speed. The H22a4's CKP is at the crank. The f20b's is in the distributor. You need either an OBD1 ecu or install the H22 oil pump to the F20b.

A Blue Lude

Yep.

Or a JDM OBD2 ECU will also work.

Prelude_5g00

Alright thanks guys!

A Blue Lude

But by all means call up your shop and confirm that's how they wired it. But it sounds like it.

hondaguy20