From what I understand, suppressing the code with the JB4 does just that, suppresses the code. Now the DPFix actually manipulates the signal coming from the sensor before it makes it to the JB4 or the DME.
It is thought that the DME uses the secondary O2 sensors for A/F closed loop control, particularly the long term fuel trims. That is why it is not recommended to keep the DPFix in place all the time.
Last edited by ajm8127; 09-25-2012 at 06:34 PM.