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Hi John,
I have a little more information to share on this.
As I suspected, you and I are basically saying the same things here, only I am confusing things in my explanation. But here are the things that I know, and I consider being statements of fact, along with the source of the facts.
The PCM controls a lot of things, such as Fuel and Ignition System, and Emissions Monitoring, and a whole host of other functions.
The two we are interested in, F&I and E are affected by which of two major ?modes? of operations, Open Loop and Closed Loop the engine is in. (FSM)
During Open Loop Modes Emission and F&I are managed exclusively via a set of Open Loop VET Tables which are certified by the Manufactures to produce acceptable levels of emissions to the Smog God?s. (FSM & Chrysler Engineer)
These tables and any adjustments to these tables are a part of this certification.
The ?Adaptive Memory? or PCM Flush/Flash that I mention does indeed happen exactly as I have described it earlier in this post. The first 50 warm up cycles and it is set forever. This process is used, and certified by DC with the Smog God?s to account for the rather large sensor variances that exist between any two sensors, and how all the Jeep sensors work together as a ?System? to maintain the Certified Open Loop VET Tables. (Chrysler Engineer)
Sensor variances can be as much as 30% as published in the FSM. (Chrysler Engineer)
Given one sensor can be 30% less then optimum, and another could read 30% more then optimum, this ?system calibration is needed. This is exactly how the DC engineer explained it to me today. This Sensor System Calibration is a part of the Open Loop Emission Certification that DC has to have to manage Open Loop Emissions to the Smog God?s satisfaction. (Chrysler Engineer)
In addition to this I asked for and received a clarification on the O2 sensors and short and long term fuel trim.
Here is is:
Open Loop modes are managed ONLY by the tables after receiving input from all the sensors (ACCEPT the O2 sensors). There is NO Short or Long Term Fuel Trim performed during Open Loop Mode. (Chrysler Engineer)
Short and Long Term Fuel Trim happen only in Closed Loop Mode. (Chrysler Engineer)
In this mode the O2 sensors are the major player in determining the correct A/F ratio and lowering emissions. There is indeed a PCM table maintained for Closed Loop operations for Long Term Fuel Trim. This table is indeed adaptive and changes over time to help manage the lowest emissions, but only in Closed Loop Mode. (Chrysler Engineer)
This is I guess where the confusing has come from.
This is indeed an ?adaptive memory table?, over time to manage the injector bandwidth. However it is a different table then the Open Loop 50 cycle table I mentioned before.
That said I have another piece of the puzzle too. The ?Official Chrysler Procedure? to flash the PCM into fast learn mode does indeed ?Clean Out? BOTH the ?Adaptive memory? (Used during open loop modes) I mention at the start, AND the Long Term Fuel Trim Memory (Used for the closed loop mode.) (Chrysler Engineer)
Also this Long Term Fuel Trim Memory, just as you described, does indeed continue to evolve to address changing conditions over the life of the vehicle.
Bottom line as I understand it, there are two major memories written to the PCM.
The Closed Loop 50 cycle sensor system calibration, as certified by Chrysler to the Smog Gods and approved, (This is what I was referencing without fully understanding it.) (Chrysler Engineer)
And
The adaptive Long Term Fuel Trim memory,used ONLY during Closed Loop Modes and continuously adjusted. (Chrysler Engineer)
I also found out that this Long Term Fuel Trim memory is adjust by using values recorded in the last 40 (forty) warm up cycles. When cycle 41 is recorded, cycle 1 is dropped from the calculations. (Chrysler Engineer)
Some other info I managed to get is that all 97 or newer Dodge trucks (gas powered) use the same basic PCM and PCM emissions and fuel management system as the Jeep. The flash flush procedure I described will indeed work for them as well. (Chrysler Engineer)
It will not work on 95 or older Jeeps of Dodge Trucks.
Also something else new:
The Jeep PCM monitors the sensors, over time and compares the values received against the values set in the Open Loop Sensor System calibration (50 cycles) not only for Functionality (Are they working or not) but also Rationality (Does the sensor signal make sense considering everything else going on in the engine?). I was told today, this is the major way the PCM knows if emissions standards are out of whack while in Open Loop mode, being the O2 sensors signal are COMPLETELY ignored during Open Loop Modes. (FSM & Chrysler Engineer)
In other words, let say the air intake temp is at ?x? and the coolant temp is at ?y?, the PCM expect the map to be at some value (range) of ?z?. If it isn?t, if it comes in as an ?a? it doesn?t make sense, and the PCM sets the MIL light.
Kind like going wheeling in Johnson Value and expecting your Jeep to be more then a bit dusty when you get off the trail, but finding out it is really covered in mud! Sure it?s possible, maybe 3 days a year, but highly unlikely. Therefore it doesn?t make sense. Put the MIL light on.
Management of the air fuel ratio while in any Open Loop Mode is via the Certified VET tables. NO, CO and other bad stuff are removed from the exhaust via the oxygen stored in the cat converter. (FSM & Chrysler Engineer)
It is only during Closed Loop Operations that the O2 sensors tell the PCM to dynamically change the injector bandwidth. (FSM & Chrysler Engineer)
How much that bandwidth is changed is dependant of another set of tables, that continuously change and become fine tuned over the vehicles life cycle, for the two Closed Loop Modes of Idle and Cruise ONLY.
I think this adds some clarification to both of our points. There are indeed memory tables that continue to change over time to reflect most current conditions, and yet there are also memory tables, which are changes once (or until flashed as described) in the first 50 warm up cycles.
Now the question becomes, ?Of how much real value is it to flash flush the PCM to reset those Open Loop Tables?? I don?t know the answer to that one.
Perhaps time will tell.
Feedback I have received says it makes a differance but how much is atributed to the 50 cycle tables vs. the long term fuel trim tables (40 cycles) I don't know.
Have a great night my freind,
Frank
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