Factory O2 Heater Relay Location?

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Factory O2 Heater Relay Location?

Postby tom_kauf » Thu Jun 29, 2017 8:32 pm

Does anyone know where the factory O2 sensor relay is located?

The Parts Diagram says it is supposed to be here (top position of the relay stack on the passenger side):
Image

But when I check there, that position is blank (no connector or any wiring there at all). I don't see any relay of that size on the driver's side either.
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Re: Factory O2 Heater Relay Location?

Postby bigBADbenny » Fri Jun 30, 2017 12:51 pm

A quick google suggested it may be powered by the main relay... or not.

http://www.subaruoutback.org/forums/66- ... 029?page=3

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from MY07 FSM html version... https://www.dropbox.com/sh/q14befxu25nx ... WHZ_a?dl=0

This is interesting: shows a breakdown of ACC, IGN and "other" power supplies...

Screen Shot 2017-06-30 at 13.15.03.jpg
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https://www.dropbox.com/s/2pqzut2o6wyqs ... e.pdf?dl=0
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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Fri Jun 30, 2017 5:33 pm

Thanks Ben! It would be good if it was powered by the main relay, because that one is definitely there.

That second diagram is interesting too!
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Re: Factory O2 Heater Relay Location?

Postby bigBADbenny » Sat Jul 01, 2017 12:43 pm

this looks interesting:

Screen Shot 2017-07-01 at 12.21.45.jpg
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That page shows the ignition circuit schema :)
IG2 ftw!
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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Sat Jul 01, 2017 12:52 pm

Looks good :). I'll see where the Service Manual says the IG2 relay is. Because the IG2 and Unit IG2 fuses got power with the Ignition. That makes sense though, since they are the fused 12V power wires, not the relay control signal wires.
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Re: Factory O2 Heater Relay Location?

Postby bigBADbenny » Sat Jul 01, 2017 1:29 pm

looks like the cabin fuse/relay box under the dash, drivers side.

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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Mon Jul 03, 2017 2:13 pm

Pages 1243 onwards of the Service Manual (EN(H4DOTC)(diag)-17) nicely list all the ECU outputs with Engine Off (Ignition On), and Engine On. None of them are usable for what I'm after. Even the factory O2 sensor heater relays don't get steady power with the engine on, they get a 'Waveform' :shock: .

I had even removed the cabin fan assembly to get to that Main Relay on the passenger side. It only got a few volts DC (maybe because it was actually a waveform, and not a steady voltage).

So my solution: I made my Windeband O2 Sensor into a mobile unit. I put a bung in the top of the Dump Pipe's sensor location, so it's removed for everyday driving. Then every few months when I do some logging, I re-insert the Wideband into the Dump Pipe. Then connect it straight to the battery and go for a drive.

The alternative would've been to get an AEM Wideband Unit, which don't blow their sensors. But I have a booking on the Dyno in 7 days, so that's pushing it. And I only just bought a new Sensor for the Innovate Unit, so it'll last a while if I only use it occasionally.

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Re: Factory O2 Heater Relay Location?

Postby bigBADbenny » Tue Jul 04, 2017 1:58 am

You can use a fuse tap & body ground connection (ig2, cabin fuse box) to switch a relay in the portable unit.
Assuming manually switching it being tricky :P
Been wanting to do same in conjunction with a tailpipe adapter, considering I have a couple of innovates spare :)
An LC-1 & 2 bought used/doa :P
Luckily the one in the car, an AEM 30 4900 works great.
Where'd you get the replacement Bosch sensor?
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Re: Factory O2 Heater Relay Location?

Postby RX25SE » Tue Jul 04, 2017 9:11 am

tom_kauf wrote:Even the factory O2 sensor heater relays don't get steady power with the engine on, they get a 'Waveform'

I had even removed the cabin fan assembly to get to that Main Relay on the passenger side. It only got a few volts DC (maybe because it was actually a waveform, and not a steady voltage).


Im not surprised. Sounds like the heater is driven by the ECU using Pulse Width Modulation (square wave). PWM is often used where control of current is required (light output, fan speed, throttle position, fuel pump control etc) so the heater can be backed off as sensor heats up. If the PWM is running at say 50% duty, then your voltmeter will only see half the switched voltage. eg: 12v@50% will show 6v, 12v@75% will show 9v etc. The frequency of the switching will not effect the output.



tom_kauf wrote: So my solution: I made my Windeband O2 Sensor into a mobile unit. I put a bung in the top of the Dump Pipe's sensor location, so it's removed for everyday driving. Then every few months when I do some logging, I re-insert the Wideband into the Dump Pipe. Then connect it straight to the battery and go for a drive.


This is probably a better option as these sensors do have a limited life.
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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Tue Jul 04, 2017 10:07 am

bigBADbenny wrote:You can use a fuse tap & body ground connection (ig2, cabin fuse box) to switch a relay in the portable unit.
Assuming manually switching it being tricky :P
Been wanting to do same in conjunction with a tailpipe adapter, considering I have a couple of innovates spare :)
An LC-1 & 2 bought used/doa :P
Luckily the one in the car, an AEM 30 4900 works great.
Where'd you get the replacement Bosch sensor?

Yeah, true. But I'm now happy with my fully portable setup :). And they say it's also not good to have the Sensor in there without having the heater on. So it's not easy to have it physically installed but fully disconnected.
I can lend it to friends if they need to do logging. And I put a long 2m power cable onto it, so the gauge reaches into the cabin. There are now ring terminals for easy connection to the battery terminals (with a spare set of nuts, so the main ones don't have to be undone).

It does mean the Heater Control is fully manual (connection the the battery is what makes or breaks power). But that's perfect when it's only used for logging. No risk of leaving the ignition on somewhere, or then shock-cooling a heated sensor wen starting a cold engine.

I got my sensor direct from Innovate Motorsports. Mine is the Bosch LSU 4.9 type, but some older ones have the 4.2 model. On their website they want US$93, but their Amazon account still has them at US$70 :D .
https://www.amazon.com/Innovate-Motorsp ... B013UG0MUS

56% of Reviews are 1 Star lol (an average of 2.5/5). That's because they like to burn out. The replacement Bosch sensors for AEM have much better reviews.
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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Tue Jul 04, 2017 10:19 am

RX25SE wrote:Im not surprised. Sounds like the heater is driven by the ECU using Pulse Width Modulation (square wave). PWM is often used where control of current is required (light output, fan speed, throttle position, fuel pump control etc) so the heater can be backed off as sensor heats up. If the PWM is running at say 50% duty, then your voltmeter will only see half the switched voltage. eg: 12v@50% will show 6v, 12v@75% will show 9v etc. The frequency of the switching will not effect the output.

Ah ok, interesting. Makes sense - I read the page I posted above after I made the measurement with the multimeter. So once I realised it was a waveform, I didn't go back with my old Oscilloscope and see what type it was. It didn't really matter - the mobile setup is the best solution now anyway.
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Re: Factory O2 Heater Relay Location?

Postby bigBADbenny » Tue Jul 04, 2017 11:42 am

Just be aware its not good practice for wbo2 sensor health to have the wbo2 sensor in an "off" state in a running car.

Similarly I'm not sure that having the sensor "on" in a non-running car is a great idea either, eg longer than the usual free air calibration period, thus the suggestion to use a relay in the porta box to switch the wbo2 on key on/off with an appropriate trigger eg IG2.

Given you have an Innovate controller, adding the free air calibration button to the circuit would be a good idea too.
Apparently the calibration can take place with the sensor removed (free air) or, sensor installed then calibrated during a long coast downhill.

For your original sensor-destroying install, what ground/s did you use?

As I mentioned, I have an AEM 30-4900 wideband failsafe in the car, had a look at their site & they now have a version 30-4100 with flex fuel sensor, which looks tempting :P http://aemelectronics.com/?q=articles/a ... safe-gauge , pending a tuner that can utilize the FF sensor for 2.5T Libs.
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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Tue Jul 04, 2017 4:24 pm

bigBADbenny wrote:Just be aware its not good practice for wbo2 sensor health to have the wbo2 sensor in an "off" state in a running car.


That's exactly what I said in my last post :lol:.
But yeah, I agree. With it being fully removed for daily driving (and a bung installed in its place, like I mentioned), I can control when it gets connected to power when I need to do logging.

I hadn't heard about the calibration button option, thank you. But I had read about the coasting method, so that's probably what they mean (since it's not really possible to unplug the sensor while driving). I've always removed the Wideband from the exhaust to do free air calibration.

I used the Battery as the earth point.

Yeah, your AEM one should work well for you.
Oh, that's fantastic! :D Yeah, that'd be the dream - flex fuel via some sort of sensor. No Flex Fuel kits are being made for our cars with stock ECUs unfortunately. All the newer cars have the eg Delicious Tuning flex fuel kits that plug into the factory harness somewhere. But as of last year when I contacted some companies, no one made one for our cars - probably not a big enough market.
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Re: Factory O2 Heater Relay Location?

Postby bigBADbenny » Tue Jul 04, 2017 9:23 pm

It's on the way from gotitrex, probably ThrottleHappy too :)
Flex tune via sensor that is...

Goals :mrgreen:

Calibration button may be LC-1 specific, I'll look it up :)
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Re: Factory O2 Heater Relay Location?

Postby tom_kauf » Wed Jul 05, 2017 8:29 am

Ok, awesome. That would be great if they finally got it :).
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