Wiring Pnp | AEM
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Avry
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Wiring Pnp

Hello Aem,
I have few questions if you can answer me as nobody is willing to share real informations about this. I'm new to tuning but i'm trying to learn as much as i can.
I'm working on a PnP harness for my 1zz-fe Toyota Celica, to use with Aem Ems-4 and i run in some "issues".
1.) Does the VCC will have to be connected to the factory ecu pin wich is, in my case Vc - +5v to TPS, evap etc. or i will be fine just with the TPS signal wire to the ems-4 TPS pin?
I know for the MAP sensor that i will have to add i will have to get 3 wires from ems-4: sensor Gnd, map signal and Vcc +5v. But i'm not sure if i have to splice in the factory ecu harness the vcc.
2.) The 35th pin of the Ems-4, Sensor GND, same question as above. It will have to be attached on the factory ecu pinout, in my case, E2 sensor gnd, or i will have to use it on it's own, just from the Ems-4 to go to the MAP only?
3.) Finally the MAF!
As i will have to add a MAP, in order to use the EMS-4, but i will have to keep the MAF for the intake air temp. sensor, will i have to disconect the maf wires and keep just the intake temp. sensor or it will be ok to keep the MAF connected as well?
4.) What wire gauge i will have to use with the ems-4, as the ones i have are in bad condition? Is it awg 18? Also, I'm thinking to go with Raychem race spec wires or you recomand something else?
I attached the pdf if it helps.
Thank you very much!

AEM_NS
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If you're building a harness

If you're building a harness to plug the EMS-4 directly into your stock OEM Celica harness, then you need to connect the EMS-4's 5v and sensor ground pins to all 5v and sensor ground circuits in the Celica harness.  And, all sensor will at least reference sensor ground so look closely at the Celica wiring diagram to see where sensors like intake air temp and coolant temp get their sensor ground from.  If you're adding a MAP sensor, then you can either re-purpose an unused circuit like say your MAF wiring to provide 3 wires for 5v, sgnd and signal.  Again, check your Celica wiring diagram to see where the TPS and possibly the MAF get their 5v from.  There are no emission control functions in the EMS-4 so things like evap or egr can be deleted. 

You can either delete the whole MAF and just wire in a new IAT sensor or you can use the MAF with its internal IAT.  It doesn't matter if you leave the MAF plugged in because unless you wire up the MAF signal wires, they're not going to connect to anything.

As for wire, 20-22 awg TXL wire is a good choice.  Teflon coated MIL wire is expensive and not easy to work with.  Pretty much every car on the road for the last 20+ years has a wiring harness made out of TXL.  

Avry
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Thank you very for the reply.

Thank you very for the reply.
I got some info from a shop meanwhile and i corrected the wiring diagram :)
The re-purpose of Maf is a good hint, i was thinking at this too but I wasn't too sure. As for the evap 5v's, it shares the voltage reference with the Tps, on the same pin and it's hardly wired in the system, the rest of it, so probably i will leave it like that, as i understood that itwill throw a lot of errors if i delete the emission ctrl! Thank you again for the reply!

AEM_NS
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If you're completely removing

If you're completely removing and replacing the stock ECU with the EMS-4, there will be no emission control functions therefore there would be no "errors" if emission controls functions are deleted. Are you doing a piggy back install in parallel with the stock ECU or completely replacing the stock ECU?

Avry
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I will install the EMS-4 in

I will install the EMS-4 in parallel with the stock ECU, to keep other functions as well. You got me thinking, now that you've mentioned about it.
I assigned Gpio#8 for Tacho and Gpio#2 for Radiator Fan1, would those still be necessary in a parallel install, or the stock ECU will operate those?

I assigned 2 Step Rev Limiter Switch input to Gpio#3 GND=on from the option tab and Gpio#3 to 2 step from the Output Pins. Is that correct?

Also someone told me that, because the Evap and TPS uses the same pin in the stock harness for the 5v, when i will add the EMS-4 Vcc 5v wire for TPS to that pin to also add a relay as the Evap drains alot of current. Is the relay really necessary or having another 5v supply in parallel, will give enough amperage to work without one?

AEM_NS
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I'm sorry but I may not be

I'm sorry but I may not be able to answer many of your questions because AEM has never once done a parallel install with EMS-4. We have only utilized the EMS-4 as the sole engine control system. You need to check a factory wiring diagram for your car to see how these different circuits are configured but to the best of my knowledge, no evap purge solenoid would ever connect to 5v. The 5v circuit is for analog reference - it is not meant to power any device. Solenoids needs 12v and ground to operate.

Avry
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My bad, it's a Evap VPS

My bad, it's a Evap VPS (vapor sens.) So that's why it shares the same 5v pin.

From what i've read over the forums, the guys left in place the factory ecu as well. But you saing that never used the EMS-4 as a piggyback and them using it together with the stock ECU, makes me think that i just have to disconnect from the factory ECU, the Injectors, coils, cam and crank signals, the variable cam control, Maf signal, Idle control, knock signal, fuel pump and i'm not sure for the o2 sensor, and maybe the tacho? The rest of the sensors, like coolant temp, air temp, tps, speed sensors and fans could be left in parallel. Correct me if I'm wrong!

Avry
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I am back again with some

I am back again with some strange issue.
I've finished my wirring harness, and yesterday I got the EMS-4 installed in the car for the 2nd time to try to start the car with it. All the connections are good, I'm using a basemap that I configured to be for n/a, I set it to run on the MAF sensor and the stock O2 sensor. So far so good, I've got the EMS-4 to run on AemTuner 2.98 on Windows 10, I connected everything and I'm trying to get the car started, playing with Initial Crank Pulse and Crank Injector Time, My EMS-4 it is password protected.
But after switching off the ignition few times, when I switch it back on I got the message "Usb device not recognized" and I can't connect to the EMS anymore, I went to the option "Find my EMS", and it doesn't find it.
What can cause this problem? Why after I got it to work, suddenly have lost the device recognition?

Avry
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I got the connection back

I got the connection back this afternoon with AemTuner 3.2 and I am trying not to forget to disconnect the ecu from the software every time I cut the ignition.
Maybe with 2.98 I didn't payed attention and I foegot to set a password at one point, even though I had one before.
So,
I got the engine to start and run around 2500-3000 rpm with the foot on the throttle, but as soon as I release the throttle slowly, the engine dies.
I know this is kinda stupid, but I don't have a timing light, and I got it slowly to start and keep it on with the throttle around 3k rpm.
Is that meanning the timing and the ecu are synced correctly and would just be a matter of fueling or idle settings?

AEM_NS
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All it means is that the

All it means is that the timing is close enough for the engine to run - it doesn't mean it's synced. Get a timing light. How are you using the stock O2 sensor? The EMS-4 can only accept 0-5v analog inputs for O2.

Avry
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The factory o2 reads the

The factory o2 reads the voltage from 0-1.2v and the sensor calibration it's adjusted to read what the factory would show, 0v-17.5 AFR, all the way down to 1.2v-10.4 AFR  from 1.2v to 5v it goes up to 18 AFR, but won,t show those numbers as it will read maximum 1.2v

AEM_NS
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Yeah, what you described with

Yeah, what you described with a 0-1v output range is a narrowband O2 sensor which can only tell you that you're either at stoich or above/below stoich. Someone somewhere may have taken the liberty of trying to assign an AFR range to somehow work with a narrowband sensor but that isn't how it works. You can not ascertain a wideband AFR from a narrowband sensor. You need a real wideband AFR sensor and controller to get real wideband AFR values.

Avry
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Yes, I understand that the

Yes, I understand that the Narrowband will only show me rich, stoich or lean, I will get a wideband soon and I will run with that.

But what I'm more interested for the moment is to get the car to start and hold the idle, then I think I can change some sensors like O2, or going from MAF to MAP :-?

AEM_NS
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No timing light and no AFR

No timing light and no AFR device. That's like trying to ride a bike with flat tires. Get the right tools you need to correctly tune your engine and then tune your engine.

Avry
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I got a timing light

I got a timing light yesterday, I did the timing sync wizard and got the engine to idle. It's a strange thing that the fans didn't kick in, the factory ECU supposed to take care of that and it didn't, so the coolant overheated. (I was keeping my eyes on the coolant temp, but not in the last 2 min). Now I set a Gpio for the fan just to make sure.

Another strange thing it's that it didn't want to start with the MAF On, on a cold start, it did start with the MAF - Off, but with Map - On, even though I don't have a MAP.  

Is it normal to get voltage on the MAP Channel Display, if the MAP Input it is disabled?

Anyway, I will leave it for now, to get a wideband, and a MAP, seems to be a better approach with the speed density and less hustle.

andyftp
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I can answer your rogue

I can answer your rogue voltage on MAP sensor.

You'll likely see some kind of voltage on that input. It will pickup some voltage from the environment, if left floating (not connected). It's not an AEM specific thing, that's with all digital electronic devices.

AEM_NS
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All of the analog inputs have

All of the analog inputs have pull up resistors so if they're open circuit, the voltage will be pulled high.

Avry
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I understand, I was thinking

I understand, I was thinking that it have something to do with the environment, as the MAP wires were hanging on the ground, protected though, but I wasn't sure.
But what about the fans not kicking in by the stock ECU? Would sharing the sensors between both ECU's can read fake voltage, like splitting the voltage or something? I would rather let the stock ECU dealing with the fans so I can use the GPIO for something else.
I know that I can add a second coolant sensor, and take the signal to the EMS-4, but if it's another trick that could make the sensor read correct values between both ECU's I would do that.