Difference between Non Emissions and Not Reported?

[turbo_bu]

Was wondering if anyone had an explaination of why the two different choices under the DTC Process Enablers. Example - I want to go SD, so I set the MAF DTC's P0101-P0103 to anything BUT X: Not Reported and then set appropriate values under the MAF parameters, (C2901, C2904, etc..). If I had picked X: Not Reported instead of say, C: Non Emissions, apparently, the PCM does not fail the MAF, and it still keeps looking for it, thus affecting the engine air flow calculations.

If this is true, then what is the different between these two. I would have originally though that selecting X: Not Reported would turn off this poriton of the code and taken it out of the loop. Reason I am asking for the clarification, is that I am building a stand alone setup without, MAF, Cat's EVAP, etc... Just wanting to understand what all is needed and how it affects the code to make sure it is doing what I think it is doing.

[joecar]

Not Reported will not report the DTC... the PCM considers the MAF failed only if there is MAF DTC.

Non Emission will not complete the readiness tests (they will always say Not Ready).

[WeathermanShawn]

It is a critical difference in reliably failing the MAF.

For most tuners, initially allowing a MAF DTC MIL is probably the smartest step to insure you are actually in 'SD'. It is analogous to a pilot flying on Autopilot. I can not imagine flying with Autopilot on, but the lamp set to 'Do not illuminate'.

But in the tuning business, it must be the emissions requirements that make most people 'kill the lamp'.

Physically removing the MAF should set a DTC. Personally I have not tested the 'Non-Emission' setting, but I can confirm that setting the Processing Enablers to 'Not-Reported' will prevent the car from going into SD.

Unfortunately it is easy to think your running SD but in reality you are running MAF. In a regular OS you can always make the Low-Octane Spark lower than High..since in SD you run off the Low-Octane Spark. It is a good sanity check.

The ultimate sanity check to confirm MAF Failed (SD) is a DTC with an illuminated MIL.

[turbo_bu]

So for say the EVAP system, which would I chose to make sure that the PCM doesn't try to command it or use it in any calculations? My plan is vented fuel tank, with return lines and no EVAP canister.

[joecar]

The PCM will still command it, you can't stop it or the test... but you can set the DTC reporting to Not Reported to not get the DTC.

[joecar]

For running MAF-less you want the DTC to show up, so do not set the MAF DTC's to Not Reported.

[turbo_bu]

Maybe this is where I need more information: Difference between DTC Processing Enablers and DTC MIL Enablers.

Same example: EVAP canister gone.
There are several DTC Processing Enablers (P0442, 443, 446 and 449) that you could set to Non Emissions or Not Reported.
There are also several DTC MIL Enablers (same P0442, 443, 446 and 449). These are only so IF a DTC is set, that you can make is the light doesn't come on?

This is now a guess on my part, if I set a proces enabler P0442 "Evaporative Emission (EVAP) System Small Leak Detected" to _____________ and leave the MIL enabler to On for the same (P0442), then it will show Ready under the scan tool, even though it is not checking for it?

Oh and yes, Offroad use only

[joecar]

The DTC Processing Enabler allows/disallows the DTC to be triggered.

The MIL Enabler allows/disallows the MIL to turn on (i.e. it won't disable the DTC).


Yes, if specific readiness test's DTC's are all set Not-Reported and MIL ON, then that readiness test will immediately report Ready.

Disclaimer: offroad use only.


[ the GM Service Manual shows a list of DTC's for each readiness test ]

[turbo_bu]

The PCM will still command it, you can't stop it or the test... but you can set the DTC reporting to Not Reported to not get the DTC.

I guess sort of a follow up question, I noticed that in some guys tunes they will C:Non Emissions the Sensor Circuit Low and Sensor Circuit High DTC's while leaving the Sensor Performance to X:Not Reported. I understand that the low and high are looking for values that are out of range. What is the exact nature of the Sensor Performance DTC?

[joecar]

High/low indicates open/short circuit.

Performance indicates unexpected value for the given conditions.