S4 NA, SAFC-II installed using the boost sensor instead of the TPS.

I recently got around to reconnecting my O2 sensor to the ECU (it was connected to the SAFC-II on an aux input for tuning purposes). I also rehooked up my diagnostic/O2 sensor watch setup - one LED for the O2 sensor light, one for the primary error code light.

I've noticed that above 4000-5000 RPM, regardless of throttle setting, the ECU is throwing the boost sensor error code (long-short-short). I have the SAFC-II tied into the boost sensor instead of the TPS, and it's not doing anything odd that I can see - it drops slightly off 100%, but I have the stock intake system, so the pressure drop from the restriction didn't strike me as odd.

I get no errors at low RPM.

One thing that could potentially be confusing the ECU slightly is that at high RPM, I'm pulling out a LOT of fuel - I think I'm set up for -25% to -35% at high RPM (and it was still somewhat rich). Is there a chance this is confusing the ECU (AFM doesn't agree with what the RPM/boost would indicate)? I didn't think the S4 ECU was that advanced, but I've been surprised before. I'd go out and test this, but the car is redtagged right now due to a bad master cylinder.

Has anyone seen this issue before? I'd like to find out why it's doing this if possible, before just replacing parts that, as near as I can tell, are working fine.

Thanks!

-=Russ=-

 

if you disconnect the SAFC from the boost sensor does it still pull the code???

 

That's a really good question. Once I get the car running again (or, rather, stopping safely) I'll try it.

-=Russ=-

 

I suspect a burnt diode in the SAFC, but until you can test, it is probably a mute point

 

moot point?

Hopefully later tonight or tomorrow I'll have the brakes working again, then I can play with the SAFC & such.

-=Russ=-

 

i thought the safc intercepts and changes the maf box signal

 

It does. Which is why I'm a bit confused about the boost sensor being the issue. However, the SAFC-II is spliced into the boost sensor, so if it's pulling more current than it needs it could drop the voltage going into the ECU.

-=Russ=-