Hondata

hi i need some help answering some questions about wiring my aem wideband 4.9 lsu to my s300 v3 ecu. The best way possible without making loads of changes to the boards components.

i know theres a few ways to do it -
d10, d12, d14, B6.

ideally id like the keep the function of the ELD, as my ek9 is a street car.

i have a p28 0BD1 ecu:
02D011F0-1500 board

r138 is missing but r136 and r137 present. why is r138 missing on this board?
ELD is currently disabled but id like to use this function.

R2 & R3 is present on the board. - this option for B6?
C42 capacitor is not present. - this wouldnt work for d12 option?

could i use the analog inputs with the supplied cable from hondata to wire in the wideband?
what would be the best way to wire this in on a p28?

ive been doing loads of searching but seems everyones got very difference ecus and either usa/jdm/edm. so many variables,
some people claim they just wired it straight to either pins without making any changes and its been all fine.

Are you planning to run closed loop from the wideband input?

Spunkster wrote: Mon Oct 12, 2026 9:00 am Are you planning to run closed loop from the wideband input?

yes i want to run closed loop for targeting AFR when cruising around and idle for better fuel economy.

You can only use the ECU inputs for this and I recommend using D10 as ELD is not needed and is available in all ECU's. Just make sure you cut the recommended resistors.

ok thanks ill go for the d10 pin

at the moment the wideband is conencted to the radio power with 10A fuse (so turns off when keys out) and ground is to the chassie/dashframe where the other dash wiring is gorund.

can i leave these as they are and connect the white output wire to d10 and be done?
or do i need to wire the ground to the ecu ground pin d21 or d22?

Does the reading match without a voltage offset?

Spunkster wrote: Mon Oct 19, 2026 8:55 am Does the reading match without a voltage offset?

ok so after some googling and reading to the hondata help files...

the gauge is getting power from radio plug(turns on/off with key), as it was before i decided to connect to my hondata s300 v3.

ground is connected to the thermostat house, but not where the fan sensor switch half is which the ecu and hondata retro coilpack is ground to, the spare 10mm bolt on the second half of the housing. hope this makes sense.

the readings from the AFR on hondata looks about right to the aem gauge. but the numbers from the decimal move very erratic, ie afr - 12.[30] < this part in brackets. i think they looked alittle high so i did a -0.01V adjustment which made it look closer to the aem 30-4110 gauge.

would this erratic behaviour be because it needs to be ground exactly where the ecu and coilpacks ground? i was worried about stacking to many grounds hence why i used another 10mm bolt hole opposite the main ecu ground on the thermostat.

voltage conversion is set to - 0v=10afr, 2.5v= 15afr, 5v= 20afr. is this also correct?

This sounds completely normal.

Ok thats great thank you for your help.