P54 ECU - Difference between auto & m/t version?

We may earn a small commission from affiliate links and paid advertisements. Terms

CQB18B

New Member
A couple years ago I bought a 1996 Civic DX (6th Gen) with a JDM B18B non-vtec that looks to be maybe 1994-ish, and an SC4, 5-speed trans. I've been using it as a daily driver and it's been doing well in what appears to be a basically stock configuration. The ECU it came with is 37820-P54-900, which based on my research is for a Honda Domani (Accord?) with an automatic trans.

My question is... what, if anything, would be different between the P54-900 ECU for an auto trans and a P54-000 or P54-J00 ECU for an manual trans? Would there be any benefit to switching from the auto ECU to the manual ECU?

It may be obvious by my question but I'm new to this but very interested in the options available with this engine swap.

thanks in advance for any help/input you have.
 

CAFROG

Honda Minion
VIP
I did not think one could run an auto ecu with a manual trans. I'm stumped if your ecu is an auto.
 

CQB18B

New Member
I did not think one could run an auto ecu with a manual trans. I'm stumped if your ecu is an auto.

Apparently it can,
P54-900 ECU.jpg
I've got no reason the think the ECU is anything other than what the tag indicates and based on the info found here https://hondaswap.com/threads/honda-ecu-list.29129/
 

CAFROG

Honda Minion
VIP
I'm far from an expert but that chip with the orange spot (bottom right) is the location a chip would be. Can guys program an auto to be stick with a chip? I don't know but it seems like the only logical explanation.

A P75 is the popular ECU for your motor
 

CQB18B

New Member
I'm far from an expert but that chip with the orange spot (bottom right) is the location a chip would be. Can guys program an auto to be stick with a chip? I don't know but it seems like the only logical explanation.

A P75 is the popular ECU for your motor
 

CQB18B

New Member
Yeah, I've noticed that the P75 is frequently mentioned in relation to the motor I have. I guess I'm just a little gun-shy about paying for a different ECU model than what's there even though it appears the one I have is already modified.

The issue I've got with this one is that two of the components (two big round items in the upper-left quad of the last pic) of this board cooked last week. The car died but restarted and has run "fine" since. I can't help but think that continuing to use this ECU is a ticking time bomb for something else to go wrong and I'd like to replace it.
 

CAFROG

Honda Minion
VIP
Your chassis and wiring is OBD2A. What is the OBD of the ECU? I'd get the same OBD as the ECU but a P75
 

CQB18B

New Member
Your chassis and wiring is OBD2A. What is the OBD of the ECU? I'd get the same OBD as the ECU but a P75

Based on your threads you've been through some of this stuff, that 92 Si is sweet looking. Do you have experience with a source for ECUs that you'd recommend. I've got a little to spend but not a lot and I've been looking around on Ebay.
 

dilbeckskate

infamous
IIRC there is no difference in maps between manual and auto , if obd1 or 2 would be throwing auto trans codes , if you want to make power have the ecu socketed and go get a pro tune
 

CAFROG

Honda Minion
VIP
Based on your threads you've been through some of this stuff, that 92 Si is sweet looking. Do you have experience with a source for ECUs that you'd recommend. I've got a little to spend but not a lot and I've been looking around on Ebay.
If the ECU is toast then I'd find one.....But manual

Redline Honda Dismantler/Recycler in Rancho Cordova, CA is a place I trust. I've bought many things from them. I also like hmotorsonline.com I bought my K20R swap from them. Great service.
 

Xanatos

Village Idiot
VIP
This is one the best newbie posts I've ever seen holy crap. Props to CQB18b.

Back on topic I agree with everyone that has posted prior. I'd snag a OBD2 (96+) Integra RS/LS/GS 5 speed ECU (P75) and run that. I usually get my stuff from junk yards (car-part.com is a good site to look at listings in my experience).
 

CQB18B

New Member
So I've received and installed a USDM P75-A01 ECU and that seems to be working fine. Thanks for the input, now I just have to figure out how to nicely fit this USDM unit in the space that seems more suited for the P54 JDM ECU size
 

CAFROG

Honda Minion
VIP
Glad things are running well. The USDM ECU will fit. Those JDM ECU's are tiny. Take a few panels off to get the carpet back enough and you'll see a way to mount it.
 

CQB18B

New Member
A follow up on this topic, does anyone know if the small differences in the HP and torque specs between the JDM B18B and the USDM B18B1(?) are influenced at all by whether the ECU is a JDM ECU or a USDM ECU? I understand that the engine compression ratio is a matter of physics but some other aspects can/are managed electronically by the ECU and I would think that would influence those specs.

and again, thanks to you who have given input, being new to this it's good to know there's a place to access pooled experience and knowledge. Hopefully as I get more experience I'll be able to contribute as well
 
Last edited:

CQB18B

New Member
Glad things are running well. The USDM ECU will fit. Those JDM ECU's are tiny. Take a few panels off to get the carpet back enough and you'll see a way to mount it.

The USDM ECU fits in after removing a bracket that appears to be there for the JDM ECU.

All done with this part of the project for now
 

Xanatos

Village Idiot
VIP
If you want it to run at peak efficiency I'd get the ecu chipped and tuned, otherwise I think you would be splitting hairs between the usdm and jdm ecus. I have read that the jdm ecus have a more aggressive tune but I have no way to back that up other than hearsay. Does it seem to run any different now?
 
Top