Checking your PCM for updates

[C5NGAGE]

In recent weeks I have been chasing a few gremlins in my 98 Coupe "White Fang". I have with the help of numerous Vette buddies found that my PCM has the original GM flash code and it may be out of date. This seems to be like updating drivers on your PC. There is a GM site that offers you the opportunity to key in your VIN number and see what changes have been made since the car was built. I had 2 updates on my 98.
Now going to the dealer to get the update is also a task. I called the three local dealers here in Va/Md and found the cost to update my out of warranty Coupe ranged from $83 to $133. Ouch!
I have to get it done and will check arround, then begin the power tuning process.
I hope this is helpful to the gang.
http://calid.gm.com/vci/
Vettes Rule!
Did anyone see the Mid-Ohio Race? Did Henrincy Win?

[1FASTDOG]

John won convincingly. A bit over an 8 second advantage over Archer in his Viper.

[Vettelt193]

I suggest talking to the Corvette tech on duty to see if he will do it on the side... I am betting $20 is all it will take

[c4c5specialist]

Hi there,
It will take me approxiamately 1 hour, to correctly dowload the latest calibration on a c5. Because we must first isolate the PCM from all other modules on the communications line, by installing a special tool. Then check the calibrations, then correctly download the latest calibration, perform crankshaft variation relearn, and an idle relearn.
We charge $79 an hour.
Failure to correctly download, will be, in effect, rolling the dice, hoping you do NOT burn out modules during the programming routine, which happens more than people will admit to.
Aftermarket programming should NEVER be an option, as once you do this, you can never reburn further calibrations from GM, because you will loose your aftermarket program.
These are all facts here, allthebest, c4c5

[C5NGAGE]

I went to Criswell Chevy in Gaithersburg MD as they had the most history with my car. They charged $90 to reflash. As I was driving out to th eon ramp to 270 south about 2 miles the engine came on, read the code and it was a the same KS P-0327.
When I got home I scanned and traced a short drive. I found Fuel Trim Cell 19 is never turned on? The PCM staus in Cell 20 then hops around 21,6 and a few others but never warm ilde?????
Off course At RPM with load it runs 20% lean, 100 plus Knocks, drops timing to 15 degrees and with an ECT or over 200 is still runing in Cell 20 unless PE or Enrichment is called for.
3 therory's
1) airleak in the Intake or exhaust somewhere
2) TB or TB wiring bad
3) PCM hosed and needs replacing
I have 80,000 miles and no more warranty.
FYI 1 to 4 shift light now works again, Whoopie!

[c4c5specialist]

HI there,
You have just diagnosed the beginning of the end for your drivability concerns.
Please disregard your fuel cell numbers, as this has NO bearing on what you are dealing with. Cell numbers are only calibrations, and do NOT have any bearing on your codes setting.
You have excessive carbon buildup in your cylinders, creating the drivability, and I think, the PCM code that you are chasing.
First, your P0327 is for the front knock sensor circuit. This would entail removing the intake manifold to diagnose, HOWEVER, there is specific instructions, that if you hear detonation from your engine, you correct this condition before you proceed with the diagnostic trouble chart.
So, with that, first thing is first, you have one of 2 choices here. First, have your engine decarbonized by the dealership, for a start to the repair, OR, add a can of BG products, 44K additive in your tank, and drive the car as much as possible, until the tank is near empty.
Fuel formulations are horrific, and create all sorts of drivability concerns, however, one thing that is never thought of, is carbon buildup, which will cause knock, timing retard, and the like.
This should be your first course of action, before condemning any component.
Please keep us posted, as I am sure that we can assist in your concerns.
Allthebest, c4c5

[C5NGAGE]

Well, I would not be surprised, I guess. But why wouldn't others have come to the same conclusion that you have and so quickly?
1) your real smart
2) you have had a lot of experience with the LS1
3) both
4) none of above
I will try this out as soon as I can find the stuff, I need a tank of gas and Maggie always like to cruise.
I had thought about carbon at one time, when I was on a long trip using cruise controll, then the next day in a rush to get on the Beltway roared up to red line in 1st and 2nd to see a huge cloud of gray smoke behing me!!!! All gages were fine, no engine noise, but I always had some knock at upper RPM's. I must be driving like my dad again.
Thanks for the tip, it will certainly be cheaper than all those parts. I forgot to mention Both knock sensors had the code but I forgot the P-0332 for the rear. This would suport your theroy/Conclusion.
I like when someone acts confident, then you have hope to resolve the issues.

[c4c5specialist]

Hi there, again,
Even with your second knock sensor code, I would still follow the decarbonization first, as this is the first line per GM diagnostics.
Only after you use that whole tank, with the additive, then, we proceed with your codes, IF they reappear.
Well, to your question, I have to serve some of the toughest customers in the world. I do it gladly. I am the last line of correct repair for Corvette for my dealership. If I cannot repair Corvette effectively, and per GM guidelines, I do NOT deserve to even lift the hood of your car.
That is how seriously I take my responsibility to Corvette.
Always remember, FACT is what it takes to repair Corvette, or any car, for that matter.
Using GM service information, on the job experience, and knowledge of the cars, will enable me to do this everytime.
Please keep us posted on your outcome. c4c5

[johnl]

C4C5, I don't mean to steal the post. But I've seen a lot of other posts elsewhere about "top-end cleaners".
What are your thoughts about doing this?
Thank you
John (97 m6 C5 w/112,000 mi)

[c4c5specialist]

Hi there,
With the high mile c5 that are becoming more prevalent, there is alot of different things that affect c5 at higher mileage.
First off, regular throttle body cleanings, are important.
As far as top engine cleanings, there is really nothing recommended by GM as to prevent this concern. Fuel formulations are the worst in many years, and they will continue to worsen.
From personal experience, only 2 things will assist in the issue of carbon buildup, a dealership decarbonization of the engine, or adding additives to remove carbon from the engine, through burning in the combustion chamber.
Either way this is done, it will NEVER BE A PERMANENT FIX.
At my dealership, we use a 2 products that assist in keeping carbon build up in check, if the customer did NOT want to have the in dealership decarbonization done.
First, BG products 44K. This is a very strong product, and recommended only for use in extreme cases, as a starting step.
Once this is done, every 6 months, we use a MI3000, also by BG as this is less strong product, and can be used once every six months.
While, GM does NOT endorse these products, and usage, I do use them, and they have given very good results.
This is just my personal experience, and others may vary.
PLease take this as such, c4c5

[johnl]

Thanks for your input. My C5 is only slightly modified, and it can still rundown the track at 13.1 110 so I have no real reason to think it's having a problem. I'm just noticing a litle knock when I first put my foot in to it from a roll.
I think I'll get some of the MI3000, is it a BG product as well or should I go to GM?
Thanks again for your input.

Edit: Oh just re-read..."not endorsed by GM". I'll look around.

[C5NGAGE]

First off, regular throttle body cleanings, are important.

Any instructions for this procedure, spray on the car or remove, soak etc. ???? As GM did long milage runs wouldn't they have seen these conditions. Back to my 98 why is it not aocncern that it doesn't go to cell 19 which is the warm idle fuel trims.
Can we get these products at AutoTrax or Where woudl you reccomend looking.

[c4c5specialist]

HI there,
Cell 19 is not always for idle fuel trims, it depends on a few other parameters before it will revert to 19.
I use GM top engine cleaner on the throttle body, with a old tooth brush. Remove the air duct, push up the throttle blade, spray a little in the TB, and brush loose the carbon. Then wipe out the TB.
So, with that, GM did find this, and revised the calibrations for this.
Then, EPA changed the formulations. Remember, this engine design was originally dyno tested back in 95, when it was first made. Alot has changed since then in fuel formulations.
Also, carbon buildup has gotten progressively worse in all engines, not just Gen3.
I use the decarb procedure and additives on all engines where detonation is an issue, and the first course of action, even back to L88 big blocks, on racing fuel.
Allthebest, c4c5

[C5NGAGE]

Thanks, does the following mean we have to be more deligent and maintenance minded with our Modern Hot Rods? I have never had a GM or other Mechanic mention these things as preventative measures. Seems they are missing a chance to keep the cars in tune and making a little extra money on the service. Would a compression check tell us it is time to de-carbonize? If I find the products I will let everyone know where, how much and what happened. Seems a gap in routine maintenance. And I run my LS1 one up to red line at least 3 times a week, I guess that doesn't do the tirck like we used to say "clean out the cob webs"

C4C5 sez:
So, with that, GM did find this, and revised the calibrations for this.
Then, EPA changed the formulations. Remember, this engine design was originally dyno tested back in 95, when it was first made. Alot has changed since then in fuel formulations.

Is there new info or cals that we need now, or is the system that adaptive?

[c4c5specialist]

Hi there,
You have already your current calibration, which carries the carbon upgraded program.
Honestly, as I have stated, the MI3000 has produced excellent results, without having any major problems or issues, and it is very inexpensive. List out is about $15 so every six months, very cheap insurance.
So, I hope we have assisted in your condition repair, and please keep us posted, c4c5