***SOLVED*** Issue with AEM AFR reading & Speedhut gauge

I installed my Speedhut boost and AFR (AEM compatible) gauges, AEM wideband with Bosch sensor, with the sensor mounted downstream from the Cats. I understand that this sensor placement will slightly skew the AFR readings; however my AFR is hovering at 10 on idle and drops to 9 on WOT.

Is this dramatic of a reading discrepancy attributed to the sensor being location downstream from both Cats? Or maybe a bad sensor? Bad wiring? Wondering if anyone has heard of this before or has insight/tips.

 

I thought I read somewhere that the discrepancy would be about 0.4 drop across cats.

Some examples here - https://www.tacomaworld.com/threads...-gen-4-0-engine.454464/page-160#post-14105672

0.2-0.4 example - https://www.tacomaworld.com/threads/wideband-afr-install-help.356280/#post-9612987

 

It is.

 

Josh, do your instructions mention anything about needing a free-air calibration?

 

Negative, the sensor (I believe the sensor is the Bosch LSU 4.2) and controller unit are supposed to be pre-calibrated by AEM.

 

Here's some more info I just started thinking about - When wiring up my Speedhut AFR gauge to the AEM inline WB controller (30-2310) I ran into a bit of a snag with the wiring. I have two red wires, one white and one gray wire (after properly wiring the controller to fused 12v keyed power and grounding). I took a voltmeter to the remaining three wires - white, gray and red. Only the red had a variable 0-5v power output when the throttle was depressed. The others were >1v even when the throttle was depressed & RPMs increased. So I assumed that the red with variable power output was the correct lead for the yellow wire on the Speedhut AFR gauge.

The picture below is a little difficult to discern, but both the gray and white wires are tapped and not used. One red is connected to the fused power source and the other to the yellow Speedhut gauge wire. Somewhere throughout my research I read that wiring issues can also cause wacky readings.

 

The LSU 4.2 in a lot of cases requires a free-air calibration.

Except on the AEM wideband gauge. Even my Haltech requires it with that same LSU 4.2 sensor.

Just to be overly clear, you have an AEM wideband gauge?

***Edit*** took to long to respond.

 

@Biscuits what were your wiring diagram wires labled by color?

@josh0351 do you have a picture of your wiring diagram?

 

Correct, it's a Speedhut gauge but setup to work with AEM: http://www.speedhut.com/gauge/GR-AFWB-02/1/Air-Fuel-Gauge-Wide-Band-8-5-18-(w--warning)-(FOR-AEM)

 

Is AEM White connected to Speedhut Yellow?

Disconnected AEM grey?

Disconnected all Speedhut White?

AEM Red and Speedhut Red both connected to the same source?

All black connected to ground? Including brown?

 

The wires I'm referring to here are all from the SpeedHut gauge. Yellow wire from the gauge is the 0-5V wire which connects gauge to W/B module. Terminology is escaping me at the moment. Green wire isn't used unless you want to tie into your Throttle Position Sensor. I just protected that green wire, tied it up, and shoved it out of the way.

If you can follow me here:

Red wire in three pin harness ties into your 12v power. I ran it to an Add-A-Fuse with and extra 10 amp fuse plugged into one of the IGN ports. I don't remember what the exact port was but it's on the second row furthest to the left.

White wire in three pin harness is your dial backlight (or needle light - doesn't matter)

Black wire in three pin harness is ground.

You have another harness with an inverter. Two wires. White and black. White is gauge needle lighting (or dial backlight) and black is ground.

Easiest way to wire it up is tie white to white and black to black.

Splice white wires into a green illumination wire. Look at one of your OEM switches. Easy to splice in with zero harm.

Run black to chassis ground (that's what I did).

In my case, I ran the yellow wire to my PLX W/B module's 0-5V terminal.

 

The ONLY wire that I connected from the SpeedHut gauge to the AFR module was the yellow wire. Ultra important: it connects to the 0-5V terminal. Not 0-3V or whatever else you may have on your AFE W/B.

 

Perfect. Thank you Biscuits.

 

Looking at the schematic, the white wire on your UEGO controller needs to tie in with the SpeedHut yellow wire. Brown is not used in your application.

 

Hopefully I helped...

 

I'm gonna bust out the volt meter and do some more checking then, might be a wiring issue afterall. Speedhut support emailed me back and said I was just running rich the Bullydog tune but no way I'm running that rich.

 

Reading through what you wrote earlier, it sounds like a wiring problem.

If your truck was running that rich, you'd have noticeable power loss, and be washing oil off of the cylinder walls.

 

Hahaha helps a lot when you just did this 3 days ago huh?

 

Hell yes.

Helps even more to shrink wrap label every single wire, connection, and terminal. You really remember what's what.

 

This was it, @Torspd - I needed to ground out the brown (or red in this case) wire and connect the white to the yellow Speedhut AFR gauge (gray is capped off & not used). Gauge works perfect now and reading properly, thanks much for the assistance everyone!

Pics below of the corrected setup. Hopefully this will help someone else down the road with the same issue.

Connected the WHITE AEM wire to the YELLOW Speedhut gauge wire. Capped off the gray.


Grounded out the BROWN/RED wire, along with the BLACK ground wire that leads to the AEM controller.


Soldered the connection (AEM WHITE with Speedhut YELLOW).


Wide-view of the final product.


Zip-tied everything in place.


Another pic of the AEM WB controller and vacuum boost connector (green on the right)..


AEM WB controller (left), wiring, and vacuum boost connector (green in the middle).