98 ex dlc scanner will not link to ecu

Justinmaccc

New Member
Ive done a pretty extensive amount of research on this problem and decided to post here when all else failed


i have a 98 civic ex that I've owned for two years. during those 2 years it had a b16a2 running a d16y8 engine harness and it always would read codes fine without any issue. about 3 weeks ago it spun a bearing and i found a b20b for cheap. so put the b20 in the car with an obd2a p75 ecu running the b16a2 hydro trans. the car was reading codes fine for a few hours after the swap and running the engine. and I'm not sure what could have happened but it just started getting linking errors. the engine runs great and I've been driving it for about 2 weeks with a CEL that i cant check, so I've started looking into what could cause this. i also have another issue of a sporadic speedometer that I'm not sure could be related. all other gauges on my cluster work but the speedometer jumps around alot for no particular reason. i pulled off the variable speed sensor plug and the connections are a bit corroded so I'm thinking this may be the cause.

things I've done so far:

1. checked both fuses under the hood for the dome light and 12v outlet

2. checked for good grounding of my dome light

3. used a multimeter to check for good grounding of the black wires, made sure the white/red wire had 12v,checked for continuity from the blue/yellow wire to pin C8 on the ecu ( reference obd2a pinout: http://technet.ff-squad.com/wiring.obd2a.htm) all checked out to be fine. also i pulled the under side of my dash apart and checked the wires i could see.

4. I've used multiple DTC scanners including the one i used to use on the b16 and even had a mechanic friend come over and try his. neither would link.

5. I swapped in my old b16 ecu but did not run the engine and my scanner wouldn't link to it either. as i said the car runs fine with a steady CEL so i don't think its the ecu.




Is there something i may be missing? as far as I've read my dlc should have no issue linking with a scanner so I'm not really sure whats going on here. Maybe something in the engine bay that i could've disrupted when swapping the engine in? any help is much appreciated
 

Justinmaccc

New Member
it was an obd2b p2t ecu for that engine. i just used a jumper harness.
 


Justinmaccc

New Member
yes, i swapped them out, unplugged the negative battery terminal for 10 minutes to be sure that the ecu would reset and it still would not link. however i did not run the engine and I've read that this may cause issues with the reset? even my cheap $15 scanner always worked with that ecu.
 

Justinmaccc

New Member
i meant to add that to my post, my apologies. i know i can read the codes using the obd1 paperclip method but id prefer to have the ability to use live data. Also my emissions is due so i will need the dlc to connect to the ecu. So far I've used 3 different scanners. my cheap one that I've always used, a $40 scanner i bought from amazon when this problem first occurred, and my mechanic friends expensive scanner. i don't really think the scanner is the issue here.
 


Justinmaccc

New Member
as my post stated, my code reader was reading fine with the p75 ecu initially. but something happened and now it will no longer link.
 

Justinmaccc

New Member
you're right, i misread your post smh. unfortunately i don't have another honda readily available to test but i know that the scanners that i have used are in working order by testing on other make vehicles and they very well should work on hondas. no i have not checked either of those, but wouldn't i have blown a fuse if pin 8 was shorting to ground? i will check continuity as soon as i can. i appreciate your help, sorry for being a d**k haha.
 
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