CalEditor

iTrader: (1)

I have documentation that states it learns TDC

edcmat-l1

iTrader: (10)

I know you like to argue, so I'll bite.

1: Regardless of any documention you have, the computer obviously knows enough to synchronize itself regardless of a case relearn being done or not. Part of that would obviously have to be knowing where #1 TDC is.

2: Straight out of "THE BOOK"

Circuit Description

The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more than an expected amount, the PCM interprets this as a misfire. The interval between CKP sensor pulses is extremely small.At high engine speeds, slight variations in the following components make misfire detection difficult:
This little tidbit is important. This is the whole reason for the procedure. It's why you have to slowly increase the RPMs until the computer cuts it.

Crankshaft
Reluctor wheel
CKP sensor

The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position System Variation Learning Procedure again.^^^^^

Engine diagnostic misfire is not operable when the engine is above 1000 RPM and DTC P1336 is set.
^^^This here is what most guys like you misunderstand. Misfire detection is inhibited WHEN THE CODE IS SET, not when it is turned off.

When the learn procedure is in progress and the engine speed is at 4000 RPM, a decrease in engine speed will occur. During the engine coastdown, the PCM monitors the CKP sensor signal and stores the pattern. This pattern is used to determine if the crankshaft speed variations are due to misfire.

And from a later model GM vehicle:

The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight build tolerance variations in the CKP sensor, crankshaft, and CKP sensor position. The calculated error allows the engine control module (ECM) to accurately compensate for reference period variations. This enhances the ability of the ECM to detect misfire events over a wide range of engine speeds and load conditions. The ECM stores the Crankshaft Position System Variation values after a learn procedure has been performed. If the actual crankshaft position variation is not stored within the CKP compensating value look up table, then DTC P0300 may set. If the CKP system variation values are not stored in the ECM memory, or a proper ECM power down does not occur after completing the CKP Learn Procedure, then DTC P0315 sets.

It's apparent the procedure is to CALCULATE VARIATIONS IN CRANK POSITION. No where does it say it's needed to synchronize #1.

Do I need to post scope shots? Or dyno graphs of cars with the codes turned off versus Case Relearn done?

While part of the Case Relearn MAY be that #1 TDC is recognized, it's not the intent of the procedure, nor is it needed to OPERATE PROPERLY. I have NEVER seen any measurable gains or benifits from performing this test versus turning off the code. And as I posted a few paragraphs above, turning the code off DOES NOT INHIBIT MISFIRE PROTECTION.

CalEditor

iTrader: (1)

From the GM information I have. It learns TDC and the variance of the engine between the cylinders. 3° off of TDC is still 3° off.

Is it posible that you could look at the code in the bin file and prove your statement?

edcmat-l1

iTrader: (10)

So post your GM info.

While we're at it, how exactly would running it through the case relearn, tell it exactly where #1 TDC is? All it will know, is the position if the #1 cyl. reluctor wheel slot. Doesn't automatically mean it's true #1 TDC. It has to have something to COMPARE IT TO. Remember, the case relearn is to account for VARIATIONS of the CRANKSHAFT, CRANK SENSOR, RELUCTOR WHEEL. Any of those three can be off enough where true #1 TDC CANNOT be determined.

As for looking at the bin, yes I have the capability to look at raw code. You're not the only one. I have IDA PRO. Also have WinOLS (not that it helps in this case). I'm half way decent at disassembling hex. And, I doubt there's going to be anything in the bin that will tell you what the purpose of the case relearn is. Although I haven't spent the time to look.

baezi z06

iTrader: (2)

i´m not an expert, but my car ran like a crap, fuel cells where allways way off although i was tying to calubrate VE and MAF, always showed misfiring on 2 cyl.

i was seeing up to 25% diffrence between banks and and much diffrence between inj. freq.

But something happened after case learn :

It stopped getting misfiring in my logs like it did on #3 and #2 and cell´s and inj. got even....



this all killed one motor for me on only one year,
Got it rebuilt..... so now i´m glad that it´s solved this huge of an problem....

thanks HPT

Baezi

edcmat-l1

iTrader: (10)

Case learn can't fix fueling errors bank to bank. It just can't.

CalEditor

iTrader: (1)

Could you explain that?

edcmat-l1

iTrader: (10)

If it needs 'splainin to you, you need to turn in your certifications.

CalEditor

iTrader: (1)

Jist havin some fun.

edcmat-l1

iTrader: (10)

I know......Me too.....