The AEM that I have has two plugs that go into the back of it. I haven't tried but it looks like you can reverse them and put them in the wrong position unless your carefull. Mine read an average of 13.2 - 13.5 jumping all over the place. Today I put the next smaller jets in my carb and now it reads 13.4 - 13.6 still jumping all over the place. I don't know if it's broken or not. I think a jet change would make a bigger difference in the reading or AFR.

Yeah Doug with a carb the gauge will jump around quite a bit so you kind of have to figure an average.  At wide open throttle it should be more steady and if you have a nice flat road and cruise control you can probably get a more stead read at steady state.  EFI should read fairly steady Stoic on cruise control and will attempt to hit the programmed AFR at WOT.  But having the gauge makes the WOT tuning much easier.

Mine also had two connectors...a four pin and a six pin and they won't interchange.

BB

Last edited by Bullet Bob (3/26/2020 8:17 PM)

Weird thing is my sensors are mounted about minus 15 degrees,works just fine, I'm carbed though.
 Obviously FI has to be much more accurate.

MS wrote:

I guess the good news is you must be getting outta this world gas mileage!

True, butt the price of pistons keeps going up.

Bob, is this the one you have? https://www.aemelectronics.com/files/instructions/30-0300.pdf

Could it by chance be in lambda and always reading 1.0? Maybe change it over to AFR?

Or is it always reading like 20:1 or something?

This is an AEM 30-4110 with the Bosch LSU 4.9 sensor.  I've been back and forth with AEM twice.  Have tested two different gauges with three different sensors on two different wire harnesses.  All combinations behave the same way:  On power up they indicate 14.7 (1.0) for a couple of seconds.  Then...apparently as the sensor heats up...the gauge steps right on up to full lean (18.5 and 1.25) and then displays the three bars. 
This is the behavior in the car and on the bench when performing AME's recommended "rag test" with a rag saturated with BrakeKleen...Sal loves that stuff but it ain't workin' here.
I have rung out the six pin harness from the sensor to the gauge but I don't have a skizzy.  Butt (TS&T), like I said, I got the same behavior with two different harnesses.  I have checked voltage to the gauge...never less than 12.3.  I have checked resistance to ground from the gauge to the negative post of the battery.... 0.9 ohm.
I noticed that red can BrakeKleen is "non-flamable and got to thinking that maybe that changed since AEM made their video so I tried the rag-test with gasoline....no joy but now my shop stinks like gas.  I used to like the smell of gas but now it just stinks.
I will say that none of the sensors they sent were in an original Bosch box...all came with the gauge.  And, I don't recall seeing any ID on the sensors as to model ie. 4.2 or 4.9.  The gauge has an analog and digital readout and can be set to display AFR or Lambda in the digital section and I have tried both settings...again, no joy.  I have driven the car thinking that it needed a road trip and it just displayed full lean with no change. 
Right now I have an email off to Modern Auto Performance, where I bought the thing, detailing what I've been through and requesting an RA.  They have closed their retail store but apparently have bodies to take care of online orders and tech questions.
I've been diddleing around with this for two months now so I can have a tool to help me do some EFI tuning...not required but definitely easier.  
If I don't get some success pretty soon I'm likely to become upset.
Thanks for the suggestions guys.  I will see if I can find a skizzy and also check for the correct sensor.  The instructions warn against other Bosch six-pin sensors and indicate that the plug is unique for the 4.9.
If I could make the damned thing work on the bench I would suck it up and try to determine what I have done wrong on the install, but hell, there are only two wires to connect to the car...one red 12V...and one black...ground, and I've verified about ten times that they are properly laid down. 

BB1
 

https://static.summitracing.com/global/images/instructions/avm-30-4110.pdf

After reading the instructions for use with just the gauge by itself.
Sounds like it should be easy.

Red+
Black-
White and blue just tape up individually

Then connect sensor.
Then select P0 (afr) or P1 (lambda)...both use 0-5volts

After two months of this?
You my friend have more patience than I would.
Especially after reading instructions.

We’re they all made on Friday or Monday? 😜

Send it back.
Sorry pal.

Last edited by Nos681 (4/07/2020 10:42 PM)

Well been doing a bit of research and it seems there are a lot of folks highly pissed over this item.  Lots of DOA reports with dissatisfaction over AEM responses.  One guy says he finally bought a 17212 Bosch sensor at O'Reilys and that fixed it.  From what I can find, the 17212 is the LSU 4.2 and the 17025 is the 4.9.  AEM says the 4.2 will not fit the connector and will not work with the 30-4110 gauge/controller.

About to try a different brand.  Maybe I'll get my $$ back....maybe not. 
Starting to get miffed!

BB1

Found an actual photo of the Bosch 17212 on eBay.
Looks like the correct plug for application.
Don’t know about the pinout.
Hope this helps.

Appears to be used with Dodge diesels.

Perhaps you could take resistance measurements from one locally and compare to your sensor.
Maybe at factory it was pinned incorrectly.

Last edited by Nos681 (4/08/2020 9:45 AM)

Nos681 wrote:

Found an actual photo of the Bosch 17212 on eBay.
Looks like the correct plug for application.
Don’t know about the pinout.
Hope this helps.

Appears to be used with Dodge diesels.

Perhaps you could take resistance measurements from one locally and compare to your sensor.
Maybe at factory it was pinned incorrectly.

That will not fit the connector on the 4.9 harness.  The 4.9 connector is squared off at one end and according to AEM it needs a different controller.  I don't know what that guy on Amazon was talking about...maybe he just bought a replacement  17025 (LSU 4.9) and got the number confused with the 17212. 

BB1
 

They might be different sizes too possibly or different kinda pins.

Last edited by Nos681 (4/08/2020 10:29 AM)

The Diesels use a different sensor.  It should have a "D" suffix.  Diesels need a wideband type sensor because they can run extremely lean AF ratios (100:1 at idle), but this extreme variation in AF ratios requires a slightly different sensor (they can hit 20:1 or less under high load situations).