Cat removal

[GMPX]

Let me try to explain the differences between a cal flash and a full flash.

The PCM flash memory is split up in to sections, Operating System and Calibrations. The Operating System contains the program that actually runs the engine (much like Windows runs your PC), the calibrations control how it is run.
When tuning a vehicle you would normally only ever need to perform calibration reflash as that area contains all the tables you see in the tuning program. When you do a Full reflash both the operating system and calibrations are flashed in to the PCM.

We sometimes hear people say that the PCM did not take the reflash correctly, or no difference was felt. Without diving in too deep all I can say is there is many steps involved in programming the flash memory of the PCM, it's impossible to 'sort of' flash the PCM, it either flashes in 100% or your car doesn't start, it's a simple as that.

Cheers,
Ross

[pjaneiro]

Let me try to explain the differences between a cal flash and a full flash.

The PCM flash memory is split up in to sections, Operating System and Calibrations. The Operating System contains the program that actually runs the engine (much like Windows runs your PC), the calibrations control how it is run.
When tuning a vehicle you would normally only ever need to perform calibration reflash as that area contains all the tables you see in the tuning program. When you do a Full reflash both the operating system and calibrations are flashed in to the PCM.

We sometimes hear people say that the PCM did not take the reflash correctly, or no difference was felt. Without diving in too deep all I can say is there is many steps involved in programming the flash memory of the PCM, it's impossible to 'sort of' flash the PCM, it either flashes in 100% or your car doesn't start, it's a simple as that.

Cheers,
Ross

I understand all that, so could you explain then why after my reflash, some options from my last flash are still there and some of the new ones are there ?

an example is my cat removal flash, on my stock pcm (flashed - tuned) i had that option re-enables meaning i now want my pcm to tell me when my cat is bad, well it never does, and that even after removing the whole 02 sensor, i had all the codes disabled in my previous flash, in my new tune i had them re-enabled, well, no go....if i take my spare pcm (stock tune) as soon as i turn the ignition on, i have p0420 and the code for o2 sensor heater fail, just that tells me indeed the flash did not take correctly...

I used to flash eeproms with a programmer, and some of them i had to erase with a uv light, even after days some of the chips would just not erase completely. Also i'm just saying it's maybe a particularity of the p10 pcm, i've got confirmation by a gm dealer that if i were to have a california approved pcm i NEED to change the whole pcm and cat (obviously) as the OS and the cals are not the same wich i would agree to because it seems the cals don't play nice with the california pcms, i have 2 pcms my original and a spare, if i take the part numbers on both pcm my spare is a federal emmissions pcm and my original is a carb, also the cals don't seem to be the same between years, if you take a stock 2002 pcm the g1021 is set 8v (efilive default) but if you take a stock 2003 set to 11v,

I'm just saying something should be checked closely as how efilive checks its transfert, on the p10 thread there's even someone saying that even after he disables the p0420 dtc he still gets the cel appear, just there is proof that not everything gets applied properly...

[Doc]

Hello,
I am not really sure about all of the particulars of your vehicle and tune but with some more details I am sure the answer can be had.

You removed the cats....are the replacement exhaust pieces welded, clamped? Are you positive the system is leak free?

[pjaneiro]

There is only one cat, and it's been replaced with a dynomax resonator, it's been welded there for the last year and half, i have no issues with the cat...I am inquiring about how to regain the low end i've lost since the removal of the cat and how to regain the 1 -2 mpgs i lost in the process also, but another problem has occured since the last tune, the fact that the tune does not get burned to the pcm is irritating me....

[joecar]

Remember that one or more complete drive-cycles are required to trigger the non-continuous tests...
when these test trigger, any tests which fail will then set DTC(s).

A drive-cycle is a specific set of throttle/load events that trigger a particular test;
each non-continuous test has its own drive-cycle, but a generic drive-cycle may trigger most of the tests.

[pjaneiro]

I usually drive 150 miles everyday, and start the truck 10-15 times a day, (Tech on the road) I am sure that this is more than enough to trigger any kind of event

[Chevy366]

The reason for a full flash is that i am starting to doubt the reliability of efilive when it come to flashing just the cals, i've read a few posts and experienced myself now that some pcms might not take teh flashing on teh first shot, even if it says so, i've had my pcm flashed and i am strating to beleive something failed somewhere, as i still have some options that are not ticked...

with a full flash at least i could be sure that i do indeed have a working flash or not...works or does not...

I noticed on a P12 a full flash still needed a calibration only flash to reset correctly , but that was at the P12 early stages .
I asked the same thing about the Custom OS not completely being removed when doing a full flash or vise a versa , maybe read the .tun from the PCM make changes and then calibration only flash .
Check your AFR and see where it is running , to rich is as bad as lean , either can cause lose of power and MPGs .

[joecar]

I usually drive 150 miles everyday, and start the truck 10-15 times a day, (Tech on the road) I am sure that this is more than enough to trigger any kind of event

Distance and number of starts are not the requirements...

Here is the generic GM driver cycle from the EFILive scantool user manual:

General Motors' OBD-II driving cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be
done in under fifteen minutes.

To perform a GM OBD II driving cycle, do the following:
• Cold Start. In order to be classified as a cold start, the engine coolant temperature must be
below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at start-up. Do not
leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
• Idle. The engine must be run for two and a half minutes with the air conditioner on and rear
defroster on. The more electrical load you can apply the better. This will test the O2 heater,
Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
• Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until
88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics
will be performed.
• Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time
the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
• Decelerate. Let off the accelerator pedal. Do not shift or touch the brake or clutch. It is important
to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the
EGR, Purge and Fuel Trim diagnostics will be performed.
• Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same
diagnostics as in step 3.
• Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time,
in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be
performed. If the catalyst is marginal or the battery has been disconnected, it may take 5
complete driving cycles to determine the state of the catalyst.
• Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or
brakes or shift gears.

© General Motors Corporation

[joecar]

On the F-body I have seen the idle catalysts monitor trigger as follows:
- at warm up temperature,
- steady speed at 40+ mph for 3 minutes,
- decelerate,
- brake to a stop,
- idle for 20+ seconds;

the idle cat monitor then manipulates the AFR and times the response of the rear O2's wrt to the front O2's... if the response time is too short it throws P0420 and/or P0430...

if you view a log of this, you will see a very clear AFR transition during idle.

[joecar]

The cursor is right where the MIL came on for DTC P0420...

Immediately to the left of this, you can see the AFR being manipulated...

Follow HO2S12 as it reacts for a failed cat... with no cat it would have matched HO2S11.