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Wiring aem wideband gauge to ecu

EFI Wiring Fundamentals

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ive had some issues wiring my aem uego wideband gauge to my link g4plus ecu, ive ran the white 5v analog + wire and connected it to my original o2 sensor wire in the ecu as my car did not have an o2 sensor. So I’ve added the aem wideband and connected it to the ecu. The wideband gauge reads normal lambda, a bit rich at idle 0.9 on e85 but on pc link after configuring the calibration my lambda 1 reads completely wrong. Could this be due to not connecting the analog - to the ecu ground? I was told I don’t have to connect the brown analog - so I only ran the analog + but on pc link it reads 0.020/0.100 so very inaccurate. Any info is appreciated

i had this issue recently with the same wideband wired up to my ecu masters emu.

what i found is this:

1. use the same exact ground point the ecu uses (common ground)

2. check the ecu settings for the fuel type, gasoline with 10% ethanol has a different stoich than pure gasoline. this threw me off big time because when changing the fuel type in the software i saw no immediate changes in AFR readings. I had to restart the software to see this change. Of course this is dependent on my software in particular but worth noting.

3. use something like an innovate 2 wideband tailpipe sniffer to compare the afr readings and tell what reading out of the two is more accurate. when i did this i found that my lambda on the ecu software was dead accurate to what we saw on the innovate wideband and that my actual gauge was a bit richer than the actual value.

4. i know the signal voltage range is 0-5V - 10-20 AFR however i had to play with that setting just a tad bit to get it to read and scale properly in the ecu software. I know thats a work around but it does work for me.

after making some tweaks to my software settings and pairing the grounds together from ecu / wideband / engine harness , changing the scaling and somparing with a separate sensor it seems that now I have consistent and accurate readings across the hardware and software.

Thanks David so I think the ground wire is pin 46 on my ecu, basically just solder it into that wire along with what ever it’s connected to? I’ll have to check the fuel type senntings in the ecu but it’s not currently running on closed loop and I’m scared to run on closed loop untill I get it sorted

G'day Alastair.

Definitely wire the analogue negative to the sensor ground of your ecu.

Can you post up your ecu pclink file? I'll just have a quick look at your calibration setting.

What’s the best way to wire it up to my sensor ground? Just run the wire to the ecu and solder it to the ground wire currently in place? I’ll post the tune file as soon as I’m home, thanks Zac

I could never advocate solder, if you can use an open barrel crimp it'd be a better way to go. Best way would be to de-pin the sensor ground pin from the ecu connector. Remove a section of insulation from the sensor ground wire around 50mm back from the pin, and crimp your gauge analogue negative to it, then slide a piece of dual wall heatshrink over the pin, up to the splice and recover it in place the seal the splice.

If you've only got a soldering iron and some electrical tape though, then you've got to use what you've got on hand, and if you're tidy about it, it'll be okay in the medium term, but I'd look at revisiting it down the track.

Can I cut the sensor ground wire about 15 cm up from where it enters the ecu and then crimp the wire from the aem gauge into it like that? I’m just trying to do it as professional as possible but I’m a little scared to open up the ecu to remove the pin, appreciate the feed back

Yup, that'll be fine.

You wouldn't have to to open up the ecu to do it the other way, just unplug the connector and remove the pin from it, and its only to make it possible to get the heatshrink in place without completely cutting the wire.

If you do cut it though, you can get the heatshrink in place without needing to de-pin anything. Just make sure its crimped back together solidly :-).

I would ground it to the ecu ground , not sensor ground . I just did this on my ecumasters emu as well.

Joe - Have you got a reason why you'd wire it to the ecu power ground instead of the sensor ground?

Because it's a gauge, and not a sensor. The gauge reads the sensor and outputs a voltage.

"Because it's a gauge and not a sensor. The gauge reads the sensor and outputs a voltage."

It is effectively just a 0-5V analog signal to the ECU. For the ECU to accurately measure a "voltage" it needs to reference the same ground as the device that is generating that voltage. Since the OP has a gauge that has a dedicated analog/signal ground then this is its reference so this needs to be connected to the ECU sensor ground which is what the ECU references from. If you use any other ground there are potential for offsets and these cant be calibrated out as they change with electrical load.