Help with wideband install

Hello everyone! I'm considering getting a wideband to aid in e-tuning but would like to understand what the installation of one is like before I take the plunge. I haven't been able to find an 5G LGT specific guide or information so I'm hoping someone here can help out. I'd be happy to write a nice "how-to" guide with pictures to help out our little community afterwards.

 

So getting down to specifics, the tuner is recommending this AEM wideband:

 

AEM 30-0300 Wideband Sensor Controller

 

The plan is to replace the rear 02 sensor in my Nameless DP with this. Since the rear 02 is only used to verify the cat is functioning, this wideband can be wired up to the rear 02 signal wire and the tune can be adjusted so the AP displays the AFR reported by the wideband controller.

 

Below is the direction I was given by the tuner:

 

Wideband install involves 4 manual wire connections: switched power, power ground, signal out, signal ground. The sensor plugs into the wideband gauge so you don't have to wire it manually.

 

The accessport will be able to display data from the wideband in addition to the stock front o2 sensor.*

 

The wideband sensor installs where the rear o2 sensor was

 

I think this basically looks like this:

 

Wideband sensor ---connects to---> wideband controller with supplied connector

Wideband controller --connects to--> switched power/ground

Wideband controller --connects to--> signal wires

 

I can turn wrenches no problem, but electrical work always gets me a bit nervous. Wiring up the power is no problem, I did that when hard-wiring my radar detector. But does anyone know what is meant by "signal out" and "signal ground"? Are these found in the wire for the stock rear 02? I don't have the FSM in front of me and I'm not sure schematics would help me much anyway if such information was presented there.

 

Help me, friends!

 

 

 

 

 

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Take a peek at this: http://www.aemelectronics.com/files/instructions/30-0300.pdf

 

The wires in question are in the harness on the right side of that first picture on Amazon, and it looks like you'll be using red (ignition power), black (chassis ground), white (output signal +0-5VDC), and brown (output ground). The brown and white wires are going to be what send the signal out to whatever logging solution you're using.

 

Step 1 is going to be grabbing yourself a wire stripper/crimper from your local hardware store- this one is what I have, but you're looking for something that'll strip wires and crimp connectors down to 20-22 gauge. While you're there, grab something that includes crimp-on spade terminals (clicky) with the red plastic coating, since those are the size you'd need. I'd snag one of those add-a-fuse taps from your auto parts store of choice (like this, just not as many) and a 5A fuse

 

As far as assembly, crimp that add-a-fuse on to the red wire, and crimp one of those spade terminals onto the black wire. When I installed my Podi gauge, I plugged the ignition power add-a-fuse into position 27 in the inside fuse block, which doesn't have anything in it from the factory. I don't remember where I installed the ground wire, but there was a screw somewhere in the vicinity of the fuse block that looked like a good candidate, might have even been one of the mounting screws for the fuse block. There's a grommet on the firewall that pokes through right above the pedals and is easy to get to from the engine compartment, so that's probably where I'd suggest passing the wideband harness through- stuff the little plug through from the outside, and you probably won't have to take anything apart.

 

As far as the signal wires, how are you planning on logging AFR? I think the standard procedure is to kill off the rear O2 sensor code in the tune, and either log AFR with a standalone unit, or delete the TGVs and use one of the TGV sensor ECU inputs to log AFR via an Accessport (it logs voltage, convert that to AFR in Excel). Depending on how long that harness is, you may have to either cut back the jacket so you can push the brown and white wires out to the engine compartment to hook into the TGV sensor connector, or buy some extra wire to run out there. Haven't done that before, so I don't have any specifics to offer there.

As far as the signal wires, how are you planning on logging AFR? I think the standard procedure is to kill off the rear O2 sensor code in the tune, and either log AFR with a standalone unit, or delete the TGVs and use one of the TGV sensor ECU inputs to log AFR via an Accessport (it logs voltage, convert that to AFR in Excel). Depending on how long that harness is, you may have to either cut back the jacket so you can push the brown and white wires out to the engine compartment to hook into the TGV sensor connector, or buy some extra wire to run out there. Haven't done that before, so I don't have any specifics to offer there.

 

It is my understanding that the rear 02 sensor input would be used for the signal but I could be wrong. I've read that that or the TGV input as you suggested is typically used.

That very well could be, too. Like I said, I haven't actually installed a wideband before, so I'm just guessing on that part. If your tuner doesn't have any more specifics, I'd bet a large sum of money that someone with a WRX has done a walkthrough on installing this particular setup, and I'd imagine it'll be the same process.

One thing that has occurred to me is if my v2 AP is compatible with this logging method. I've come across this nasioc guide that mentions using a v3. Logging AFR with AP v3 and AEM UEGO - How to wire it up.

Anyone have any thoughts? Note in the screenshot the AP v3 is showing "Sensor Only Rear 02". I don't remember if that is a selectable display item on my v2.

Asked my tuner about the v2 vs v3 AP thing and it turns out the v2 can still work. It just can't display the calculated AFR and some manual conversion of values is required by the tuner after they get your log. It does have me thinking though, since Cobb is still doing the trade in program, it may be worth the switch. There is no way I'd get $325 for my v2 selling it to someone else. If I hold on to the car for another few years it may be worthwhile.

 

So I'm going to buy the wideband and hope that I can figure the rest out. I also bought something like this from Amazon: Oxygen Sensor Receptacle Kit. It is a bit of a gamble but I think I'll be able to come up with basically a plug & play solution with this. The OEM sensor and wiring would be completely disconnected and hopefully I can connect the wideband with this. At least the sensor wires anyway, maybe not power.

 

And again, if anyone can help decipher what wire is for what in the rear 02 pig tail, that would be super helpful.

When I replaced the rear O2 sensor on my Baja, I bought the sensor that came without a connector (saved $20 or $30). From what I remember, there's a white wire (signal), one wire that's not white (sensor ground), and 2 more wires that are the same color (heater). I'll try to dig that up in the Legacy vacation pics and let you know if it's the same (and maybe do better on the wire colors...)

Hokay, here's what I found:

 

 

The red wire in position 2 is switched power (comes out of the O2 sensor relay, which is both powered and activated by ignition power), and the blue wire in position 3 is the signal (that dashed-line cylinder is shielding). I think the orange wire in position 4 is going to be the signal ground, since that wire joins up with a lot more sensors further downstream and goes to a common pin on the ECU, and that would make the pink/blue wire in position 1 your main (heater) ground. The diagnostic tree for P0420 seems to support that, since it tells you to check for 0.2-0.5V between pin 3 and chassis ground, as well as resistance across pins 3 and 4. The heater is controlled by the ECU switching the ground wire, so position 4 really can't be for the heater.

 

Kind of a roundabout answer, but I think that covers it.

Perfect, thanks a lot! So it sounds like blue in position 3 goes to wideband white and orange in position 4 goes to wideband brown.

 

Parts should be arriving this week and I can hopefully begin installing next week.

So these aren't the wire colors I was expecting. No red or orange. Am I missing something?

That's the sensor, right? The red, blue, orange, and pink/blue would be in the car-side harness. Can't say I've looked at the wires on the rear O2 sensor on my Legacy, but the crimp-it-yourself Denso replacement I bought for Baja had the same color wires- the two black wires are for the heater (not polarity dependent), blue is signal, and white is ground. I know positions 3 and 4 are swapped between the Baja and the Legacy, but if that's a Denso sensor, I'd bet you'll find pink/blue > black, red > black, blue > blue, and orange > white (car side > sensor side).

 

 

I knew there was a reason I didn't throw away the old O2 sensor or the installation instructions when I changed the sensor a year and a half ago...

Ah, that makes sense. I just pulled off the sensor and was looking at that scratching my head. Didn't think to check the other side.

Update on this - everything went perfectly with the install and e-tuning. I'm very pleased with how the wiring for the signal turned out since I used a new connector. The rest of the wiring was a piece of cake since I used one of the add-a-circuit things. No wire splicing necessary. The worst part of the whole process was getting the two wire harnesses through the firewall.

 

When I have a chance, I create a how-to thread for this.

Just reread this thread and realized what you were doing. I had no idea you could use the rear o2. I always thought you could use the AP with the wideband only if you did the TGV deletes and used the wiring from there. So the tuner just has to tune out the error code the missing o2 sensor would give?

Just reread this thread and realized what you were doing. I had no idea you could use the rear o2. I always thought you could use the AP with the wideband only if you did the TGV deletes and used the wiring from there. So the tuner just has to tune out the error code the missing o2 sensor would give?

 

Yep, there were I believe three codes that were thrown when I removed the rear 02 sensor completely. A map update took care of those as well as allowed the AP to show and log the wideband voltage. I could have gone with TGV approach but I didn't want to chop up wires. Going the rear 02 route, I was able to use one of those oxygen sensor receptacle kits linked a few posts up. Made for an OEM-like install and I can easily uninstall it all when the time comes.

I suppose the other thing to add about the rear 02 is that since I only have two bungs in my downpipe, it made sense to hijack the rear 02 wiring since that sensor would be removed.

Can you post a picture of the connections ? Im going to be installing a wideband but I will be retaining my rear o2 sensor and just tap into the signal wire just trying to figure out which wire I need to tap into.

 

 

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Link to how-to

https://legacygt.com/forums/showthread.php/wideband-install-277478.html