Hondata

Has anyone came across a problem where the map sensor reads +boost while the key is on engine is off? I'm having an issue with a 95 EG sedan, b18b1, p28 with an s300 v3, 4 bar map. Ever since getting everything swapped from my EG hatch into the EG sedan ( re used EVERYTHING besides the chassis harness from the hatch. The Engine harness, ecu, trans, engine, shift linkage, fuel tank with pump and fuel line, the steering column and ignition cylinder/key.) Everything else works on the sedan, head lights, tail lights, blinkers, dash lights, etc. For some reason though the map sensor is reading 29psi with the key on, engine off, so whenever I go to cranking its just flooding itself with fuel trying to feed that 29psi. I've checked an oem MAP sensor and replugged data in, re uploaded the tune, and the same scenario happens. I've tried another p75, oem map, injectors and same thing still. I've had the engine harness out now numerous times checking continuity and the pinning from the ecu to their respected spots/sensors. D17/19/21 check continuity from the ecu pigtail to the sensors actual F input and shows good. ground is at G101, cleaned and reconnected a lot of times now hoping.. I'm out of ideas now with it to try, any input would greatly be appreciated. I've also tried another working main relay to rule that out. the only thing I have NOT done is try running 3 wires from the ecu pins to another pigtail cutting the original 3 in the process. ( i can solder/head shrink )

Have you tried the ECU on a known working vehicle to see if it reads the MAP sensor correctly?

I’ve tried another ecu from a running car and it done the thing as the p28 s300 is doing, I’m not able to try this ecu on another car with my 4bar yet.

IT may be a wiring issue, but if a MAP sensor is wired incorrectly, it will damage it instantly and you will have to replace MAP sensor as well.

I had changed out the distributor and map sensor pigtail today, the car actually fired up and revved etc, it did have a code 9 though, i left and came back to button up everything and it’s back to the same problem from before , no code 9 now just 16psi + on the map reading, injector pulse seeing 18-19ms. Instantly flooding

If you put the stock MAP sensor back on and change the setting in the software, does it read normally?

Sorry for the late reply, it doesn’t. it still reads positive boost, when I unplug it, it maxes whatever settings I have it on, wether it being stock, 3bar, 4bar. It does pick the sensor up though plugging in and unplugging it. I’m at loss anymore lol

You need to try your ECU on a known working vehicle as it sounds like you may have your vehicle wired incorrectly. Use the calibration for the vehicle you test in.

tried ecu in another car, and everything worked good. sorry it took so long to get a reply in, life won't stop long enough for me to actually post.


back story, the engine and trans, harness and all was used in a 92 hatch, had it tuned and all then swapped it into the sedan shell, now having these issues.. The identical setup was just running/driving etc. nothing was cut on the harness, simply just changed chassis. from ecu pigtail to the actual sensor shows continuity in all correct places even. stomped still. gonna order another harness and see what happens

so while datalogging yesterday with the key on engine off, map sensor reading was scattered all over from must moving the connector itself on the map sensor, I was able to cockeye it halfway on/off and it actually read correctly, then when fully plugged in it read wrong. Going to be digging into that today. also the hondata isn't showing any errors but I am getting a code 9 from the check engine light, i'll toss another dizzy in there while i'm at it today too. update will be in just a couple hours.

Well she’s finally alive. Ended up changing map sensor pigtail from ecu to sensor, got an oem map sensor new, got everything together, wiped calibration on s300 and started with a basic p74 basemap. Added in my data for injectors and such but the map was only showing -2psi , I got it to start and finally just kept it running and it started reading more range within 5min of keeping it running, started sounding healthier and running better the more it ran. Got it to idle and now it’s reading full range. I was able to reload the tuned file back with changing the map sensor parameter and drove it for the first time last night. 💙 thanks spunk for some insight and trying to help!

Unsure if there was moisture or blockage in the actual map port leading to inside intake or what. I have a new 4bar map sensor coming again incase my 4bar took a poop

Thanks for the update - glad it is running, and it is always good to hear what the solution was.

Thank you Hondata! I 100% had to come back and let everyone know what fixed mine just incase anyone else has to go through the same thing. It stomped me for almost 2.5 months honestly.