Originally Posted by Benn0
Well the software fix is supposedly to correct a condition where the computer is misreading the data from the sensors. So those numbers could be misreads.
Another way to look at it is that the pressure sensor will be calibrated with certain air pressure differences equaling an expected amount of soot. The difference in air pressure could just simply be greater than what the 100% calibrated value is. ie if 10psi is thought to be 100%, then 11psi is 110%.
Yes, since all the sensors (temp, pressure diff) feed into the PCM and all of the controlled components (injectors, EGR etc) are run by the software in the PCM. You live and die by the programming and the accuracy of the sensor and actuator calibration.
Let's say the calibration of the differential pressure in across the DPF is out. The sensor might only trigger the active regen only when the filter is far too blocked. (the guy the "kinked" capillary tube had the same effect from this mechanical problem)
If the EGT sensor is out of calibration then this will effect the EGR commands. If it reading a higher temperature than actual, then the PCM will operate the EGR to cool the combustion = more soot.
A similar story with the EGR valve. I assume it has an actuator(?) and a position feedback. If there is a mismatch here then it could effect the operation of the EGR. Again, if the EGR is set for too much recirc = cool combustion = more soot.
Even if the sensors themselves are calibrated correctly (and independently) there might even be errors in the scaling of the readings to the PID value seen by the PCM. Wrong data in = wrong sequence out. (Garbage IN = Garbage OUT my boss always says).
I've had a look at some of the standard PID's, pretty complicated and there are plenty more proprietary ones Chrysler wont show us.
Another factor is errors in the programming, not so much "bugs" but inappropriate setpoints for the operating conditions, and the possibility of unsuitable events occurring the sequence.
example: An active regen is triggered "drive at highway speed" and then only seconds later the vehicle goes into limp mode.
That's not very robust programming.
Putting in a "10minute delay" before the limp mode as was mentioned before sounds like putting a band-aid on a burst artery.
If the sensors aren't failing, and the filters aren't failing with some "sticky coating", and the oil level doesn't make a difference then it must all be in the programming.