Hello everyone. I 've bought a 92 CRX 1.6-16i (ED9) about a year ago and i'm just in love with it. It has a factory D19A9 in it but has no cat. Idk if it was removed or never was there to begin with. It has a PR4 OBD0 ecu with modded chip on it which is not its original ecu, i think they switched to be able to modchip. Today during oil check i noticed one of the two wires of cam sensor is broken, but car still runs fine with no check engine light. Does PR4 support such sensor? Engine light itself is working i think bc it lights up for a couple seconds when i turn ignition on. Should i repair it?

 

cars with D16A9 did not have a cat and therefore didn't have an O2 sensor - instead, they had an IMA sensor - the correct factory OBD0 ECU for the D16A9 is a PM7 with IMA sensor which is the thing on top of the ECU, like the attached picture - the number on them would be 37820-PM7-B0# - the PR4 ECU will run the engine too rich since it was originally for the B18 engines

you should definitely reconnect the wire for the cylinder sensor on the exhaust camshaft - the sensor determines the position of the no. 1 cylinder for the proper function of the sequential fuel injection - with the disconnected wire, you should have a code 9 showing on the ECU - have you checked the ECU for codes? the codes are stored in the ECU - when the ECU detects a problem, the Check Engine Light will come on an code will be stored - once ignition is shut off, the Check Engine Light will go off and stay off until another problem is detected, however, codes from previous Check Engine Lights will remain in the ECU until you physically delete the codes by resetting the ECU - just because you don't have a CEL doesn't mean there aren't codes stored - with the PR4, I would think you would also have a code 1 for the O2 sensor since you don't have one - I do not know if there are European PR4 ECUs that have an IMA - none in the U.S. do

 

Thanks man you're the King. And sorry i was mixing a8 with a9 about cats. PR4 has an eeprom with slot as opposed to PM7, and my chip is definitely not original so i assume it has some kind of tuning on it but, it does smell gas when driven on high revs so its possibly running rich anyway. I plan to mess with maps a bit down the road but its not my current issue.

So you're saying CEL will go on only the first time a problem occurs and stays off after ignition restart even if the problem persists? That's bad. And PR4 being o2 driven is even worse So if i clear ecu with hazard fuse i should get CEL the first time i turn ignition on. I will try that.

So i should replace ecu to an IMA driven one or add cat and o2 sensor. Are there any other options? Also any further info on IMA sensor would be nice. I will check codes and take note of ecu's exact model to check what kind it is.

 

you should get a CEL and a code every time the ECU senses a problem - if it senses a problem that it already has a code stored for, the CEL will come on but it won't store the same code again - you won't get a bunch of the same code for multiple CELs that come on

remember that OBD0 D-series ECUs do not have long and short flashes, only short - just count the number of times it flashes and then pauses - a code 14 will flash 14 times, etc.

 

Should i short the diagnostic cable? Or just turning on ignition is enough? My problem is CEL is off all the times except for first few seconds of ignition, indicating no problem while having a broken sensor wire and possible missing o2 sensor. I think i should be getting pretty solid cel for cam sensor alone but nothing. I wonder what other secrets it keeps from me I will try getting code at first chance and post here the situation.

Also is it possible to add o2 sensor to a car? Maybe modifying exhaust a bit without adding a cat?

 

So i checked some things. ECU is 37820-PR4-Y00 idk if that would tell anything about it. Like what model and possibly trim it came with or if its ima or o2 type maybe.
I do have an ima sensor near ecu but idk if its being used or not. I also have a "service jumper" under passenger side dash that shorting makes no diffrence as far as i can see.
I looked at red led on ecu and it blink shortly 1 time when ignition is opened and again blinks one time when ignition is turned off, seems normal to me but is it an error code?
I tried to trigger a CEL by disconnecting throttle position sensor but it didn't came on which is weird isn't it? It's like ecu is stuck in safe mode or service mode or smt.

Also should i ask this in engine management topic maybe more people will see? Truckload of questions, thanks a lot to anyone who even reads them.

 

if it were mine, I would try to find the correct PM7 ECU for it - where are you located? - I found some on ebay in the UK

 

I'm in turkey and i think finding a pm7 would be hard and expensive for me. And PM7's don't have socket for eeprom so i can't mod its maps so not preferable. Drilling and welding a socket for an o2 sensor would be easier i think, if that would work, doing manual work by myself of course. My problem is ecu seems to be stuck in some no fault condition and doesn't warn me about anything. Also a bit help on reading codes.

 

If the motors stock why would you want to mod the maps anyway? The car will run great on a PM7.

Disconnecting the TPS wont throw a fault necessarily but it will prevent you from revving over ~3k when driving