What's up guys? I have been away from the scene for a bit and have recently started working on my car again. I am just finishing up a rewire and tuck and need to verify my PLX wideband wiring. The setup is an S300 P28. Let the dead horse beating begin!!!

I currently have the PLX wired as follows;
Red- to ecu power.
Black- to ecu ground.
White- wired into D10
Grey- wasn't connected to anything

Now I know all of that is correct but I would like to utilize the grey wire as well. If I am to do that I would wire the same as above but also add the grey to the D14?? I have read numerous threads but can't seem to get it straight. Is there a benefit to running closed loop off of the grey wire? It is my understanding that closed loop will provide the best driveability and gas mileage. My plan is to unplug my stock o2 sensor (which is downstream form the PLX sensor) and tap into the D14 at the jumper harness in order to get the signal into the ecu. Once that is done I assume I just switch to closed loop and the D14 input in the Smanager and run off of the PLX signal, going back to open loop and the white wire D10 input for tuning and datalogging? I hope this all makes sense. I feel like I am complicating things too much and hope someone will be kind enough to set me straight. Cheers,

-Ryan

 

you should never run a heated o2 sensor controller's ground wire to the ecu ground, it will cause horrific interference and can drastically confuse the ecu at times.
run the ground to a solid chassis ground or engine ground.

 

Really? I was under the impression that you wanted the wideband to share the same power and ground source as the ecu. I am pretty sure I read that on Xenocron's wideband integration page, I will double check. EDIT--> Right here http://www.xenocron.com/install/Xenocron-Wideband-Setup-Guide.htm Thanks for the heads up.

Does anyone have any info regarding my question? Maybe I am just better off running closed loop off of the stock sensor and forgoing the grey wire all together?

 

I'm not familiar with the PLX setup, so I can't help you with that, sorry.

I do know though that almost all wideband companies make it quite clear not to tie into the ecu ground wire. they do however suggest using the same ground LOCATION as the ecu or the engine sensors.

which means:
DO: attach the wideband ground to the engine harness ground bolt. this is the ground for the ecu and engine sensors. but you must attach it to the BOLT, not the harness wires
DO NOT: splice into the ecu ground wire in the harness, or any other ground wire anywhere in any of the harnesses.

 

Point taken. I didnt seem to have any issues but it makes sense. Thanks for the advice.

Now I just need someone to help with my original question.

 

Apprently my memory works better when I'm hungover lol; I almost forgot: with s300 you can now run closed loop even with a wideband signal, no need for a narrowband signal. you can keep the wideband signal at d10, or you can run it to d14 instead considering that's the stock o2 input. so really, you don't need the grey wire. just make sure to check the box for "disable o2 heater circuit" in the closed loop tab.

 

Sweet, thanks. I def cannot relate to the hangover comment however. I couldn't be farther from the opposite lol. Thanks for all of the help! Looks like I will be unplugging the stock o2 and the PLX grey wire and running closed loop that way.

 

Just curious, other than the resistance through the length of the wire between the ECU Ground bolt and where one might splice in, what is the difference here between splicing in, and putting the ground at the bolt?

 

honestly chris, I have no clue personally lol. most wideband manufacturers who's documentation I have read in depth though have stated things regarding electrical noise/static that affects the ecu if tapped into the ecu ground wire, but does not affect ecu operation if it's tied in directly at the bolt. almost as if being at the bolt causes the engine or chassis to act like a damper or absorber in a similar way to how the car battery acts for the power side for the alternator noise/spikes.

 

google search for ground loops

 

wow, very interesting. I just read like 10 very informative descriptions of ground loops, and have definitely learned the actual science behind it. so yeah, that would most definitely have quite an impact on ecu operation if the ground for a heated o2 system is tapped into the ecu's ground wire instead of a solid chassis or engine ground. good reads, thank you

 

I don't see how this could actually happen, and further a 'solid chassis ground' just doesn't exist, unless you are physically sharing it at the same point as the battery's ground. A chassis, especially on a Honda with seam-sealer left and right, is going to introduce all sorts of unwanted variants, and potentially noise from different offsets through the body of the car.

The G101, main 1/4" ring terminal ground on these cars is simply a common ground point for:
-ECU's power grounds and logic grounds
-Digital sensor grounds (B-Series = F. Speed, K-Series = F. Speed, Engine -Hall Sensors, etc)
-Your shield drains are spliced from the factory to logic ground, which in turn shares multiple joints with ECU power ground both internally at the ECU and at G101 acting as a a splice.

The 'engine sensors' are grounded through a regulated Sensor 0V at the ECU, while VTEC, VTEC PSI, Knock, etc are physically grounded by mounting the component to the cylinder head/block.

How does connecting a conductor to a bolt vs one of the other conductors terminating to the same bolt differ? The only thing that could come to mind is a resistance change due to the age of the existing wiring on the car, but you are not physically grounding the wideband here, you are providing a ground for the controller. Also, most aftermarket EMS that are capable of controlling a wideband directly, must have the sensor's ground tied to the main Sensor 0V for the ECU.

How exactly is a ground loop anything to be considered here? You are sharing the same 12V and 0V from a device that's wiring can withstand ~15A with another device that will not pull any greater than 2-3A of in-rush and typically <1.5A at normal operation, there should be NO offset or resistance change. If you were providing either 12V or 0V at different points, ok you'll potentially get an offset. You're really meaning to tell me that either device is going to cause a significant voltage drop to the other? This is 12/14.5V, not 600V. If the wiring is in good condition, it's not going to happen.