Hondata

Hondata s300 V2
Hasport socketed P72 but I think it is a clone
PLX Wideaband O2
Those are the pertinent items.

For most of my testing, I am using the ignition on run with the car off. That gives me pure air for a reading on my AFR of 20 or 5v. I have taken voltage readings between all ECU ground pins and D14 which I was using for wideband input and come up with 5v give or take .03v. I have the PLX wired to A25 and A24 for power and ground. There is no voltage differential between A24 and D22 when everything is running. I have increased the size of the ground from A24 to the thermostat housing (G101) just to be sure. Power as read on the wideband and multimeter with the car on run but not actually running is just over 12v and is higher when running. When I read the ECU sensor display, I get 3.81v at the most. I changed to pin B6 to be sure it was not the input since the voltage at the ecu pin was reading 5v on my meter. The new pin still reads low. Now for the tricky part. If I start the car, I can plot a linear curve from 0v to 3.81 which corresponds to the actual voltage which should be read of 0v to 5v. I can simply account for this in the software but I would rather solve the root issue. Has anyone, any suggestions?

Forgot to mention. I am using the latest Beta version of 2.3.2.0 but also had the trouble with 2 other versions I updated from trying to make sure I didn't have a bug. S/N on the s300 board is 22448. I just started using it although I purchsed it some time ago. Warranty expired before I had a chance to test it cause of other work needing to be completed. Any uploaded calibration will result in the same issue. It is in a 93 Civic dx with JDM OBD2 GSR motor but evap solenoid is maintained. All pins for the GSR motor are wired through and working including knock and VTEC oil pressure. (Replaced VTEC solenoid with USDM). Basically a USDM wiring setup at this point. All grounds have been either verified or replaced and verified in the engine bay.

If it matters at all, I had a corrupt configuration file and had to start over since I would lose most access to the ECU when this file was uploaded until I performed an Erase ECU. When I reuploaded the same config, I lost access again and had to erase. I am now running on a new config but still having the same misreading voltage issue. I deleted the old corrupt config file so I don't have it anymore. One thing the file did is change the O2 setting to narrow band. I drove for about 20 minutes I am guessing with this setting but with the wideband connected to the input. The gauge ran a little rich but not enough to do any damage. I could not upload or view sensors with the corrupt config in place. I hope it did not damage the inputs.

Isn't D14 limited to 3.8 volts?
Try D10. It should read up to 5 volts that your AFR meter puts out.

Okay, that did it. I changed to the ELD input, disabled ELD adn alternator control, removed R136 and R138 from the ECU and this seems to be working perfectly now. Thanks for the help.

You may have to play with the voltage offset to get it to read perfectly with the gauge. I usually do 0.02 at a time, positive or negative.