AFM/DOD Questions

[Marky Dissod]

A friend just warned me that here in CA at least, the scanners used for our smog emissions testing required every other year can detect if the ECU has been reprogrammed in any way from stock and will fail and flag in the system.

Your friend does not know enough of the details of what he is talking about.
Here I go AGAIN.
Long story short: pcms tcms & ecms that have been properly reprogrammed, have had their checksums and Checksum Verification Numbers properly edited so that your friend will be perplexed (either mouth agape or crosseyed) at the fact that the VAST majority of tuned vehicles have gone and will continue to go UNDETECTED.

Long story medium (a mathematician could explain this far better than I could):
Each section of the software programs that operate our engines and transmissions (as well as other powertrain related stuff) is written using coded characters.
Each character has a hexadecimal representation (26 letters + ten digits).
The hexadecimal sum of each software section is stored in a separate part of the pcm / ecm / tcm from the program itself,
as well as the Checksum Verification Number (which is more complex, involving multiplication as well as addition).

This is what the California smog test checks for when it connects to your pcm / ecm / tcm.

"the scanners used for California smog emissions testing required every other year, can detect if the ECU has been reprogrammed in any way from stock"

WHORESCHIDT

In order for that statement to be true, California would have to use HPTuners, EFI Live, Wester's Garage, or some other software
that would not only include the ability to decode shift tables, spark tables, limiters, etc, so that each program part could be compared for differences from OE,
but would need to physically download each of these.
That's not what California is doing.
They're just comparing checksums and checksum verification numbers to GM's checksums and checksum verification numbers.

An example will be shown in the next post.

 

[Marky Dissod]

VIN: 1GNEC13Z06R139635 (a 2WD PPV, yours will most likely have different CVNs)
Controller: PCM / VCM Powertrain / Vehicle Control Module
Function: Programming

ID Selected# CVN
1 12619623 0000EF26
2 12619630 0000C6B4
3 12596229 00008118
4 12591458 00009467
5 12606607 0000852F
6 12591495 0000B2AE
7 12591524 00007288
8 12606773 00004C7F

There are other older CVNs that correspond to older program segments.
Newer vehicles have separate engine and transmission control modules with more program segments, checksums, and CVNs.

All California can do is inspect the checksums and CVNs for matches.
California canNOT download any of the operational software in anyone's pcm / ecm / tcm. Therefore,
California canNOT "detect if the ECU has been reprogrammed in any way from stock" - except if it was reprogrammed improperly by a retardiot,
because PROPER tuning REQUIRES recalculation of the checksums and CVNs so that they still MATCH.

How in the hell else are there so many tuned vehicles driving around in California? Nevermind the other states that kiss Cali's @$$.

 

[Jake707]

You can go to the screen on the DIC in the middle of the gauges that shows the MPG readouts and down in the corner it will show V8 or V4 mode active. The Range plug in disabler works fine on these machines. Son had a lifter making noise, scared him, he put some Sea Foam in the engine and got the Range device and it's been perfect now for 20K miles or so.

View attachment 433046

When using the Seagram did he use the digger type through the throttle body or did he suck it through a vacuum line somewhere on the engine?

 

[Jake707]

VIN: 1GNEC13Z06R139635 (a 2WD PPV, yours will most likely have different CVNs)
Controller: PCM / VCM Powertrain / Vehicle Control Module
Function: Programming

ID Selected# CVN
1 12619623 0000EF26
2 12619630 0000C6B4
3 12596229 00008118
4 12591458 00009467
5 12606607 0000852F
6 12591495 0000B2AE
7 12591524 00007288
8 12606773 00004C7F

There are other older CVNs that correspond to older program segments.
Newer vehicles have separate engine and transmission control modules with more program segments, checksums, and CVNs.

All California can do is inspect the checksums and CVNs for matches.
California canNOT download any of the operational software in anyone's pcm / ecm / tcm. Therefore,
California canNOT "detect if the ECU has been reprogrammed in any way from stock" - except if it was reprogrammed improperly by a retardiot,
because PROPER tuning REQUIRES recalculation of the checksums and CVNs so that they still MATCH.

How in the hell else are there so many tuned vehicles driving around in California? Nevermind the other states that kiss Cali's @$$.

Whole lot of info over my head so I’ll just take your word for it and sssume there are different “levels” of tuning as I know for a fact my diesel truck had an EFI live tune on it and it failed smog and flagged my vin to the state. I had to then return it to stock tune (not that big of a deal) and add back the cat etc, but then had to take it to a state referee for retesting and they made me change a few other mods I’d done that the average smog tech lets slide or doesn’t notice during visual inspection.

Not interested in going through that again or having to hot smog my wife’s Yukon so I’ll most likely just use a plug in style disabler.

 

[tooleyondeck]

$250 to toggle a switch in HPT is insane, even if $100 of that goes to credits. That being said, who's to say you didn't have your engine swapped with one that didn't have AFM and thus requiring the ECU to be reprogrammed?

May as well go with an actual delete of the system if you're paying for a tune anyway:

Texas Speed & Performance Gen 5 LT1, LT4, L83,L84, L86, & L87 DOD Delete Kit

Texas Speed & Performance Gen 5 LT1, LT4, L83, & L86 DOD Delete Kit

www.texas-speed.com

 

[Marky Dissod]

Whole lot of info over my head, so I’ll just take your word for it,
and @$$ume there are different “levels” of tuning as I know for a fact my diesel truck had an EFI live tune on it and it failed smog and flagged my vin to the state.

Diesel & gasoline are two different problems to the Caliphony Air Reseach Board, diesel being a far worse problem that is far more carefully scrutinized than gasoline.

Not interested in going through that again or having to hot smog my wife’s Yukon so I’ll most likely just use a plug in style disabler.

Clearly some stranger from NYC will not be able to assuage your concerns.
You really ought to ask Californians with GM 5.3L / 6.0L / 6.2L V8s how they get away with 'full' tuning; there are many more than you would first guess,
even if I freely admit that there are not enough of them here in this forum.

 

[Dave in Gig Harbor]

My 2018 Silverado 1500 6.2 has had a very mild stumble at idle from almost the day I got it. Took it to the Chevy dealer for a tranny service at 50k miles and asked them to look at the stumble. They said they all do that and not to worry. So I do not worry about it. At 80k, the truck bent a pushrod and it cost $5k to have the right bank fixed. Shop would not do any alterations and I was not in physical shape to heads and do the repair myself. Love the truck, but HATE the AFM/DOD. I am looking for a 6.2 engine to rework and put it in the next time something like that happens. I did buy the ranger and it stops the truck from going in to V4 mode.

 

[Gearz]

I live in NH and if I installed a tune that disabled AFM or DOD it would not pass emissions because it's looking for those engine parameters and the truck would fail. I called Diablo tuners and they couldn't answer my questions if a tune would affect OBD2 for state inspection so I use Range Technology so it diables the AFM. I think DOD would drive me crazy because I want V8 power all the time!

 

[Rygrego]

A friend just warned me that here in CA at least, the scanners used for our Smog/emissions testing required every other year can detect if the ECU has been reprogrammed in anyway from stock and will fail and flag in the system. He said I should only get the type that is removable from the OBD port and unplug it a week or two prior to testing to allow for all the systems cycle as OE designed.

Exactly as stated by your friend. I must remove my Range AFM/DOD delete about a week before the test so the cat monitors will set.

 

[Marky Dissod]

I live in NH and if I installed a tune that disabled AFM or DOD it would not pass emissions because it's looking for those engine parameters and the truck would fail.
I called Diablo tuners and they couldn't answer my questions if a tune would affect OBD2 for state inspection so I use Range Technology so it disables the AFM.
I think DOD would drive me crazy because I want V8 power all the time!

Some people are only beyond help because they do not understand why (and/or how) things work or don't work.

Whole lot of info over my head so I’ll just take your word for it and assume there are different 'levels' of tuning ...

Part of a thorough proper 'tune', includes fixing the checksums and CVNs so that when the gov't hooks up to a vehicle, the only thing they see is unaltered checksums and CVNs, leaving the tune undetected.
Those who understand this well enough are driving around with tuned vehicles - tuned TO THEIR TASTES, not necessarily to be 'faster' - that pass state emissions inspections.

Whether or not you disconnect it before the state inspection, best to keep your fuel tank between 3/8ths & 5/8ths full to be sure the EVAP system is ready soonest;
EVAP is not nearly as active when the tank is closer to either full or empty.