AEM wideband wired to my ECU through rear O2

[Staytuned]

In this thread here we discussed wiring the 0-5v wire from the AEM wideband into the rear o2 sensor input on the ECU (pin75). I wired it up today and started the car and proceeded to log the the data coming from rear o2 sensor. For the first few seconds I had a nice fluctuation of data coming in, then all of a sudden it started reading a straight 1.27v. It never moved from that number again. The air fuel gauge was moving from 14.7 to 15.3 and sometimes higher as the car struggled to keep a steady idle (it was cold). According to the AEM manual the voltage should have been reading anywhere from 2.50v to 3.27v in that AF range the gauge was showing.

Is it possible that the ECU does not read any higher than 1.27v? And once I start WOT logging it might come down. The AF ratio 11.2:1 is around .78v.

Has anyone else tried this? If so did it work? what am I doing wrong if anything?

 

[JiggahMan]

You already know the answer.. the WB is 0-5v the ECU is 0-1v it won't work period.

 

[Staytuned]

No if my suspicions are right I will be able to log AF ratios from 9.72:1 up to 12.18:1. Because those AF ratios fall between 0v and 1.25v on the wideband.

 

[JiggahMan]

Well, you just proved your suspicions wrong..

 

[Staytuned]

I like when people respond to my questions with some first hand knowledge on the topic. If you have never tried this or have no knowledge of what the outcome might be ....please do not reply to this thread. You have given me no data, no actual factual information other than it won't work.

My concern is what might be the repercussions of running a higher than normal voltage reading into the rear O2 pin on the ECU. At WOT the voltages are less than 1v coming from the wideband....should be loggable right? But extreme lean conditions (deceleration) you will see much higher voltage numbers. Is this going to damage the ECU or is it still safe.

 

[ikickuintheball]

I don't know, but with DSMlink, I have my PLX wideband output (0-5v) going to my rear o2 sensor like you do. So it should be fine, but I don't know if the ecu is going to let you do what you want since it's programmed to see 0-1v. Good luck.

 

[Staytuned]

Well it does log values below 1.27v....but I am concerned with long term affects from higher voltages going through the ECU from rear O2 pin. For me to only be able to log A/F ratios from 12.1:1 and down it is not worth risk of the unknown.

 

[Staytuned]

Instead of wiring in the white 0-5v wire I am going to wire in the blue 0-1v wire. At least that way I can log 02 values that will be more accurate and more consistant than the front O2 sensor.