Hondata

Hello,
I am running an AEM X series 30-0300 Wideband with a p72-s300.

My problem is that the AEM guage is reading differently than what the s300 is reading, AEM will read a rich AFR (12-13) while the s300 will read a lean AFR (16).

The AEM wiring is as follows:

Black wire: Radio ground
Red wire: A25 (with 5 Amp fuse)
White wire: D14 (directly connected/no splice)
Brown wire: Analog input ground on s300

I tested both grounds and all are good. The car will start and idle fine, hondata will read all the sensors but as I noticied the Lambda does not change even when I tap the throttle.

My voltage/lambda conversion table:

[.51 VOLTS/8.50 AFR]
[2.51 VOLTS/13.25 AFR]
[4.51 VOLTS/18.00 AFR]

Other parameters I have set:

Wideband input source D14
Voltage offset is 0
Closed loop wideband input (voltage)
Wideband target voltage 3.11

Please help me : (

Do not use the radio ground. Instead use a good solid chassis ground.

Do not use D14 as the input as it cannot see the full voltage range. Use D10 instead.
Details can be found at: https://hondata.com/help/smanager/wideb ... b=wideband

Spunkster wrote: Wed Jul 03, 2024 9:06 am Do not use the radio ground. Instead use a good solid chassis ground.

Do not use D14 as the input as it cannot see the full voltage range. Use D10 instead.
Details can be found at: https://hondata.com/help/smanager/wideb ... b=wideband

I was under the impression that the new 4.9 Bosch sensors can use D14 as it does not require the full 5v to work properly?

We do not recommend using D14 at any time with any sensor other than a stock narrowband.

Spunkster wrote: Wed Jul 03, 2024 9:58 am We do not recommend using D14 at any time with any sensor other than a stock narrowband.

Understood, but if I use D10 and remove the two resistors do you think that would alter or fix the ground offset?

Have you changed the ground as recommended?

Spunkster wrote: Wed Jul 03, 2024 11:53 am Have you changed the ground as recommended?

I have not changed the ground yet, is there any place you recommend? I used the radio ground because I checked it and it is very low resistance to engine/body.

Solid chassis ground or the thermostat housing is best.

Spunkster wrote: Wed Jul 03, 2024 12:55 pm Solid chassis ground or the thermostat housing is best.

Is it okay if the black wire is grounded directly to the thermostat housing? Since the ECU itself is already grounded to the thermostat. I also very much appreciate your advice and help : )

It should be ok

Spunkster wrote: Wed Jul 03, 2024 2:22 pm It should be ok

I grounded the black wire and cut the resistors for D10. Since I switched to D10, should my wideband target voltage be higher now? Right now it is set to 3.11V

I rewired and removed the resistors. The gauge now reads a lot closer to what the hondata is reading, hondata will read 17.8 AFR while the guage reads 22 AFR Is this still bad? or can I adjust voltage offset to counter this?

Just wanted to state that I solved this problem! The answer is very stupid bit I am still learning! The 01 Prelude uses OBD2A while the p72 s300 I am using is OBD1. I was using the OBD2A pinout for the wideband wiring when I should I been using the ODB1 pinout!! So for anyone wiring up a wideband with an OBD1 swap, Sensor analog +5v goes to D16 (ELD pin) on the OBD2A, which should route to D10 on the OBD1 with the proper wiring converter. To sum up, make sure to use OBD1 pinout diagram if your using an OBD1 ecu!!!