No input from Wideband into SD2

[Mike Y]

Chasing down an issue where the wideband input to the SD2 is not working. It's actually kind of flaky where it sometimes works and sometimes doesn't. The main problem is that the input from the wideband is not making it's way into the ECM and into power logger.

Powerlogger is constantly showing 8.5 and it seems when the engine goes into closed loop, it is correcting as much as it can (pulling 10.2 of fuel) from the 8.5 number to get to the target AFR (13.5).

I am using an AEM inline UEGO with a gauge, and the gauges reads the correct AFR and toggles frequently so that is a good indicator that it is working.

But at the ECM, we always see 8.5.

We have a complete SD2 setup (from a car that now has ECUGN) and we did a swap of the following one at a time:

- Swapped ECM - no Change - each ECM has it's own Powerlogger board on it
- Swapped Powerlogger Analog input board - no change
- Swapped powerlogger cable that goes from the analog input board to the powerlogger on the ECM - no change
- Swapped AEM gauge/controller - no change

in a last ditch effort we put in a fresh battery just in case a low voltage could freak the system out but that made no difference either.

We also verified that putting a signal on pin 1 would at least do something at the ECM, and it does seem to work. We just grabbed another wire from the AEM wideband and put it on pin 1 of the Analog board and saw the voltage change on powerlogger.

But the behavior is flaky, in that sometimes when the car is running the Scanmaster will start showing the AFR and it matches what is on the AEM gauge. We are not sure how it happens though.

At this point I am at loss of what it could be so any ideas or things to try would be great.

Mike

 

[EricM]

What gauge are you using with the AEM, and have you tried removing the gauge?

Do you also have the analog ground connected to the powerlogger input board?

 

[Mike Y]

Hi Eric,

its one of their Uego line. The gauge itself is the controller but we did swap it for another of the exact gauge we had with no avail.

about the ground, I can’t recall us ever connecting it up but worth trying.
Is that an internal ground for all those inputs ? I had thought it was just for that 5v supply.

Mike

 

[EricM]

Just to clarify. You said you are using the AEM Inline wideband. The AEM Inline doesn’t have a gauge. Maybe it’s not the “inline”? Which model # do you have? Some have a separate analog + and -.

 

[Mike Y]

I think I got the name wrong on the wideband. It’s the 30-300 from their uego line.

I am away from the car so can’t try the ground but I recall not connecting it and only using the white signal wire.

SD2 has been working great ever since we put it in and it just now has this issue.

maybe we have it installed wrong and have just gotten lucky with it.

 

[EricM]

Ok, got it. That one has a brown wire which is a separate analog “ground”. It helps eliminate ground offsets, and should be connected, but I don’t think it’s causing your particular issue.
I would check the signal voltage at the powerlogger input pin 1 to see what you get there.
You mentioned you swapped the AEM controller, but what about the AEM harness? Maybe there’s something wrong in there?

 

[Mike Y]

Ok, got it. That one has a brown wire which is a separate analog “ground”. It helps eliminate ground offsets, and should be connected, but I don’t think it’s causing your particular issue.
I would check the signal voltage at the powerlogger input pin 1 to see what you get there.
You mentioned you swapped the AEM controller, but what about the AEM harness? Maybe there’s something wrong in there?

The powerlogger is showing about .120v to .130v even while the wideband is showing 20afr.

the harness is the only thing that we didn’t swap since it is all tucked in but it’s one that we should try.

 

[Mike Y]

Quick update that swapping the wire harness made no difference.

What is more confusing is that while driving, I would see no AFR action on the Scanmaster (but the gauge continues to work) and then it would wake up and start working where the SM reading matches that on the gauge.

I have been setting parameters 2,3 and 4 to be 98 so that closed loop is off but uses the AFR table to get by. But when the wideband starts working we would switch those to 9.7 to run closed loop and it runs flawlessly.

Not sure what to think of next as the intermittent nature of the issue is hard to debug............one solution that does come to mind is simply just to move to ECUGN and have this all behind me.....;-)

 

[EricM]

I would disconnect the wideband output wire from the powerlogger input board, and monitor the voltage on that wire, to see if its matching up with the AFR.

 

[Mike Y]

Did some further debug on this today and for the benefit of anyone reading this that might have the same problem I did find the culprit.

Turns out it was the sensor itself. Not sure what exactly, but replacing it with a new one seemed to have brought the unit back to life.

So even though the gauge was still reading AFR properly, it seems that the sensor must somehow be tied to the interface logic that manages the button pushes and the analog output.

 

[EricM]

Interesting! Hopefully that was it.

 

[Mike Y]

Interesting indeed. I had been going back and forth with a support person at AEM, and he said that most of these issues like this come from a weak power supply.

He also mentioned that the sensor side does not have any dependency on the system/signal side.

So far it seems to be working a before but without a root cause it leaves the possibility of this happening again.