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Tuning advice

Old Aug 8, 2018, 08:43 AM
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Tuning advice

I have a 2014 GSR with stage 3 mods and a tune from Rick at My idle is a bit off when rolling to a stop so I bought an AEM Wideband sensor in hopes of getting a better tune.

The mods are:
- MXP short 3" downpipe
- Ultimate Racing HFC
- Cobb cat-back
- AEM intake
- RRE boost solenoid
- Cobb Accessport v3
- AEM Wideband

I followed these directions to log my new wideband sensor:

Epic fail!

First off, my car doesn't have yellow and orange wires on the rear O2 sensor harness but pins 3 and 4 are red and green respectively. This is to be expected as it changes over the years. So I followed the directions and grounded the green wire (pin 4) and connected the white wire from the AEM Wideband to the red wire (pin 3). Nothing. No voltage to the ECU from the wideband and no CEL.

I then read on another forum that I need to reverse this. The green wire (pin 4) should be connected to the white wire on the AEM wideband and the red wire (pin 3) should be grounded. I did this and I got voltage to the ECU! I changed the monitor in the Accessport to AEM Wideband and it looked ok at first.

But problems.

After restarting the car, I got a CEL. Code P2252. I flashed to Cobb stage 3 just to make sure it wasn't something in my tune too but that didn't help.

I tried taking the ground off of pin 3 and that code went away but now it had a different code. I forgot the code but it was something about the O2 voltage was too high. The Accessport still logged the wideband but it was off. It was .5 to 1 off from what the gauge said.

So, I disconnected the wideband from the rear O2 sensor and put it back to stock so I no longer have a CEL.

I dug up an old netbook with Windows 7 on it so I'm thinking about selling the Accessport and getting a Tactrix cable and going with an open source tune. I'm not trying to make 500 hp from this car. I just want it drivable, reasonably quick, and reliable.

- Are there "off the shelf" open source tunes I can start from and then tweak as needed?
- Should I just stick with an e-tuner to reach my goals or is this something pretty simple to do given my mods?
- Maybe I should just stick with the Accessport and I just need to wire up the wideband differently?

What do you guys think?
Jon Roberts is offline  
Old Aug 8, 2018, 12:54 PM
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The ground on your 4-pin connector should be the SAME location as the AEM gauge to prevent any voltage offset/discrepancy. Since you're dealing with 0-5v a small offset will cause issues.

p2252 indicates a negative signal is being fed. So at that point it' was hooked up backwards but with the right pins.

I'd try the wiring dance one more time and see if you can get it to work since quite a few others have had good luck.
splattj is offline  
Old Aug 17, 2018, 09:00 AM
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I got it "working" sort of but it still had a CEL for voltage too high. The rear O2 sensor has a range of 0 to 1v while the AEM has 0-5v. So, it should be expected to throw a code for too high of a voltage.

But with a CEL, it doesn't really work.
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Old Aug 23, 2018, 11:06 AM
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some wideband controllers actually have a narrowband emulation function that can output (from the gauge) an analogue 0-5v on one wire and a 0-1v on another, mostly to keep the ECU happy.
PLX wideband has this output for sure. This might solve your issue.
Zergburger is offline  
Old Sep 30, 2018, 08:05 AM
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I don't have the AEM, I have the Prosport (plug: it looks great and says "EVO" at the top), but my symptoms are similar.

The Prosport also has a 1V sine signal in addition to the 5V analog for logging. The 1V I used to pass inspection this year (I've since gotten an NGK O2 for the an actual signal), but it's useless for full range (i.e. wide-band) A/F logging.

What I find most interesting is that P2252 is for sensor 1, that's the upstream sensor, not the rear O2. So that extra voltage is clearly confusing the ECU, but so far doesn't seem to be having any other consequences.

If I want to record the A/F using the AccessPort I wire nut the signal out and signal ground from the Prosport analog cable to the ECU-end of the rear O2 harness. Then I use the "RO2 Voltage" channel on the AP for recording. As you've found out, if you don't ground it, you get a voltage offset that screws up the measurement and it does so unreliably at least for me; I found it wasn't a consistent 0.5V so I couldn't just shift my measured value and have it work. That's a shame because without the ground out, I didn't get the P2252 code (I did a lot of combinations). Also if you don't either have a real O2 plugged through the heater circuit or a 10 ohm resistor (make sure it has plenty of wattage or it will get hot) you'll trip a CEL for O2 heater as well. I passed inspection on a 20W resistor but I'd go even bigger if I didn't plan on having an actual O2 in that rear bung because it still got pretty hot.

If you or I had open source we could simply disable that CEL. With Accesstuner we are limited to a few pre-defined CEL ignores. I started with Cobb because it was easy and now I'm sticking with it because I'm not looking to do everything over again. That's a serious option for you to consider, though, and I don't want to diminish that path.

My solution is a little more trailer-fabulous. Since I'm still deep in my tuning phase, I'm leaving the 5V signal all the time for data logging. Once I'm done, I'm looking for a switch to go in one of the blanks on the center console near the AWC button. I'll be able to switch between the actual O2 and the 5V signal. You just need to cut between the signal/ground pair for either of those (5V gauge or normal narrow-band O2, but you could tie in AEM's 1V "fake" signal if it's available instead of the real thing) and a shared pair of pins out to the ECU harness. The O2 heater circuit will always be on, separately from the switch circuit because, I'm told, it's bad to expose O2s to exhaust conditions with the heater off plus it keeps that heater CEL light from popping.

I haven't found the right switch for both function and appearance, but I can ping you about that when I do if you'd like. If you search for a switch on your own, beware of "momentary" switches that always return to a "default" connection; think window rockers that always return to open (circuit, not motor drive direction) position.

I hope that helps!
the.jack is offline  

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