I have a 2004 Dodge Sprinter in my shop that will go into limp mode within a minute of driving. Codes 2026 and 2030 set for the O2 Sensor low. I have load tested the wires from the ECM to the sensor and a new sensor has been tried with no change to the issue.
This is a Bosch wide band lambda sensor which I have a basic understanding of the operation but there is little to no waveform captures of this system out there. I understand that the ECM reads the change in current which is difficult to capture at such a low milliamp range.
Long story short, this is what I have found. The waveform generated by the ECM looks normal for the first few minutes at idle. Once the sensor reaches operating temperature and the heater pw cuts back, the signal degrades. At this moment the ECM enters a limp mode and opens the VNT turbo fully.
In order I have a capture of when the engine is cold. Next, a capture from a know good running 2005 Sprinter. Then a capture of the 2004 Sprinter at operating temperature while in limp. Finally, I have a capture of the transition of the signal with the heater duty cycle plotted.