Wire with Power only when the Engine is running/starting?

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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Mon Jun 19, 2017 12:24 pm

bigBADbenny wrote:Awesome but why not use ign2?

Yeah it is definitely is the preferred option to use IGN2. I have a day off today, since I worked Sat, so I'll have time to look into it :). I just wanted to clarify the circuit, even if I don't use it.
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Re: Wire with Power only when the Engine is running/starting

Postby RX25SE » Mon Jun 19, 2017 3:36 pm

The circuit you show will need a diode to stop the relays contact circuit from back feeding the vehicles crank circuit. This potentially means the engine will continue to crank when the key is moved back to the run position.

If you are worried about the load on the circuit supplying both the control coil and the device, use the relay in your diagram to drive the control circuit of a second relay. This second relays contact circuit can then draw from the battery to power the device.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Mon Jun 19, 2017 3:48 pm

RX25SE wrote:The circuit you show will need a diode to stop the relays contact circuit from back feeding the vehicles crank circuit. This potentially means the engine will continue to crank when the key is moved back to the run position.

If you are worried about the load on the circuit supplying both the control coil and the device, use the relay in your diagram to drive the control circuit of a second relay. This second relays contact circuit can then draw from the battery to power the device.


Ok, thank you for the advice.

Yeah, that's a very good idea.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Mon Jun 19, 2017 5:48 pm

bigBADbenny wrote:IGN2 is right there in the cabin fuse box, lowest row iirc:)

I checked again, and as I thought I saw last year, it unfortunately gets power with the Ignition on (engine still off).
There are two that have similar names in my car, 'IG2' and 'Unit IG2' (which is in the bottom row).

I'll look into some of the other ideas that have been brought up.
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Re: Wire with Power only when the Engine is running/starting

Postby bigBADbenny » Mon Jun 19, 2017 6:44 pm

I'll take a peek at mine too. The issue being you have a certain issue that's burning out the wbo2 sensors? Where exactly eg distance from turbo/exhaust port and angle of insertion, and dump type, in your car?
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Mon Jun 19, 2017 10:44 pm

bigBADbenny wrote:I'll take a peek at mine too. The issue being you have a certain issue that's burning out the wbo2 sensors? Where exactly eg distance from turbo/exhaust port and angle of insertion, and dump type, in your car?

Great, thank you. Yes, I've burnt out the 1st one in about 9months and 10,000km. I was always careful not to leave the ignition on for long before starting the engine (to avoid shock cooling). But the day before my Sensor died, I was testing my new sub with the Ignition on for a while (then started the engine), and I suspect that's what killed it.

It's pretty close to the turbo (about 20cm), on the top of the dump pipe. It's a bit close, but that was the best spot for it, for accessibility and making sure it fits at all. I was concerned about heat, because the manual says at least 1m downstream, but others on Subaru forums haven't had any problems. Probably because the exhaust gases cool down in the up-pipe first, unlike NA cars where the distance from the exhaust manifold is more critical. And there is an error code that gets produced when the sensor overheats, and that has never come up on mine.
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Re: Wire with Power only when the Engine is running/starting

Postby bigBADbenny » Tue Jun 20, 2017 10:50 am

I'm going to research if anyone has had the same issue.
I know running the engine with the wbo2 "off" is a definite no no.
Running the wbo2 with the engine off is somewhat similar to calibration mode I guess...
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Tue Jun 20, 2017 11:16 am

Ok cool. I know the Innovate Motorsports Sensors fail like there's no tomorrow (a quick google search confirmed this). They are Bosch Sensors, but maybe their heater is a bit less intelligent and doesn't ramp up slowly. Other brands seem to have a better control, but I'm stuck with this one for now.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Tue Jun 27, 2017 6:57 pm

I've worked out the solution that's the easiest for me I think.
Today was the first day I've been able to work on this since last week....

I confirmed that the Secondary Air Pump (Exhaust Gas Recirculation) Relay control signal wire only gets power with the engine running :good:. *EDIT: FALSE ALARM, READ SUBSEQUENT POSTS BELOW*. And it actually stays powered for the entire time (not just on engine warm-up, when the Secondary Air Pump would usually stop after ~20sec). I went for a drive and made sure of that.

That relay is removed from my car anyway, since I have an EGR Delete (block-off plates). So instead of splicing into any wires, I can use a Spade Terminal to go into that contact, and run my Wideband Relay from there. I guess I could just put the Secondary Air Pump Relay back in, to power my Wideband directly. But that'd require a lot more splicing or cutting of the factory harness, which I'd rather avoid.

The multimeter probe in the picture below is in the contact that I'll be using. Unless I find a relay inside the cabin, which I'll check for now....

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Last edited by tom_kauf on Wed Jun 28, 2017 11:44 pm, edited 4 times in total.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Tue Jun 27, 2017 10:53 pm

No luck with any of the interior Relays. I pulled the whole assembly out and even tried the 4 or so relay positions that don't have a relay in them (for things I don't have like seat heating, but the wires are there). All either got signal power with the Ignition, or another source like a switch for that accessory eg Window Defroster switch. None were dependant on the engine running.

So I'll stick with the Secondary Air Pump relay contact. It just means I have to run another wire from the engine bay. Oh well, at least I've found a solution to this problem.
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Re: Wire with Power only when the Engine is running/starting

Postby RX25SE » Tue Jun 27, 2017 11:15 pm

tom_kauf wrote:
I confirmed that the Secondary Air Pump (Exhaust Gas Recirculation) Relay control signal wire only gets power with the engine running :good:. And it actually stays powered for the entire time (not just on engine warm-up, when the Secondary Air Pump would usually stop after ~20sec).

The multimeter probe in the picture below is in the contact that I'll be using.


Id be checking the schematic, but I suspect this wire (circuit) is driven high by a module (most likely the ECM).
If thats the case, I doubt it will be able to supply the current to power your device. You may be better off fitting a relay here to power your device. The module can supply the approximate 100mA to the relay control circuit, but more than that you may overload the driver circuit in the module.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Wed Jun 28, 2017 9:04 am

Yeah, definitely using the Relay that I've always had for the Wideband. That's what I had previously, but the control signal got power with the Ignition.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Wed Jun 28, 2017 10:34 am

And yeah, it is the ECM that controls that Relay, like you thought.

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Re: Wire with Power only when the Engine is running/starting

Postby RX25SE » Wed Jun 28, 2017 8:50 pm

tom_kauf wrote:And yeah, it is the ECM that controls that Relay, like you thought.


The schematic shows that all three air relays control coil circuits are fed battery voltage by the main relay, via (what I think is a fusible link) SBF-7.

This means the control coil circuit is completed by the ECU pulling the opposite side of the coil to ground using a transistor (ground switch). This method of driving relay coils is common, as a ground switch uses the load of the control coil to dampen voltage spikes as the relay is activated/de-activated.
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Re: Wire with Power only when the Engine is running/starting

Postby tom_kauf » Wed Jun 28, 2017 11:06 pm

Ah, ok - thanks for the explanation. That makes sense now.

Now that I've got everything back together and the Relay control wired up to the Secondary Air Pump contact, it's behaving differently :angry2:.
That contact now gets power with the first click of the Ignition, and only turns off with Ignition fully off.

Sigh, makes me look like I was dreaming the other day, but I know I wasn't.

There's probably a lot more behind the ECM's control of that line, than a simple engine on/off. I thought it might be current-sensing (ie sensing if that line is open-circuit or not). But even with my contact removed again, it still got 12V with the first click of the Ignition. Even a warm start didn't change it. Might have something to do with the ECU reset that would've happened, because I had the battery disconnected....who knows what paramaters the ECU uses for that...

Anyway, probably nothing anyone can help with. 90% of the work is done, I'll just check the other relays and find another one.
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