Cel - P0401

[MrZumma]

While on my way to work Monday morning, I was glancing at the speedometer and in that instant, saw the CEL illuminate. "Damn" I thought, not a great way to start the week..

When I got home that evening, I threw my OBD-II scan tool on it and pulled a P0401 code. I decided to check the other sensors while I was connected and noticed that everything was normal except the B1S2 O2 sensor. The Fuel Trim percentage was pegged at a positive 99.06% and the voltage for that sensor was fluctuating normally as expected. I took it for a road test and the Fuel Trim percentage never moved from 99.06% while the voltage still fluctuated as expected and within specifications.

Next, I followed the FSM diagnostics for the P0401 as best as I could, but found RT's diagnostics approach much better. The thread can be found here. After completing the diagnostics, I have determined that the EGR vacuum modulator is to blame for the P0401 in this case.

My question is this. Is it possible that a failed O2 sensor has cause the EGR vacuum modulator to fail or visa-versa? Or is this just coincidence? Either way, I think I'll be calling Dan to replace both O2 sensors and the modulator...

Thanks for any insight.

 

[MLX450]

O2 sensors pull different codes........

 

[napertuckytim]

I had a P0141 code, replaced both 02 sensors (from Cdan) and no more CEL.

 

[RavenTai]

I cannot see how an O2 problem would lead to an EGR problem or vise versa, maybe if the EGR was stuck wide open severely affecting the burn in the cylinders but that is unlikely.

 

[MrZumma]

I didn't think so RT. I'm chalking it up to coincidence..

Thanks all for your input..