PCM Relearns After any Read or Write to the PCM. LS1-Edit Strange behavior.
09-19-2002, 10:45 PM
#1
Race Director
Thread Starter
PCM Relearns After any Read or Write to the PCM. LS1-Edit Strange behavior.
Ok here is the story...I finally figured it out...
In the past I have said that my car pops and bangs loudly upon decelaration. And it did that until tonight...
2 nights ago I did a read of my PCM with LS1-Edit. Also during the read all my valet lights came on by themselves and stayed on till I turned the key off. Anyway, I did not drive the car after that . I finally had the chance to take it out tonight.
As I pull down the driveway it started sounding really wierd at the exhaust. Almost like is was missing and chugging... then it went away....and a few seconds later I got a check engine light. ( Later I checked it and it was P1518 TAC Module)
Anyway I started wondering what was happening and it dawned on me that the PCM was relearning. The P1518 Code must have set when I did not let the PCM do an Idle learn. I drove away right after starting it.
Anyway after I got back after driving about 20 miles...The popping on Decelaration was all but gone....This is weird!
I got this Info from Ken at Carputing. He said anytime the PCM is read or written to it forces a relearn.
So this got me to thinking...If the PCM is relearning, is it also relearning the idle too? Was that bad that I just pulled away? What is protocol here? How about guys who Dyno tume and upload changes after every run? Don't they have to let the PCM stabilize? Please somebody explain..
:confused: :confused: :confused:
I saw this too. It specifically states if the PCM has been written to an Idle LEarn must be done. But with LS1-Edit I guess a read causes the same condition.
Idle Learn Procedure
Idle Learn Procedure
Anytime the powertrain control module (PCM) or the battery is disconnected, the PCM loses power, or the PCM is reprogrammed, the PCMs learned idle position is lost. The engine idle is unstable when the learned idle position is lost.
Perform the following procedure in order to return the learned idle to the correct position:
Automatic Transmission
Turn OFF the ignition.
Restore the PCM battery feed.
Turn OFF the A/C controls.
Set the parking brake and block the drive wheels.
Start the engine.
Ensure that the engine coolant temperature is more than 80°C (176°F).
Shift the transmission into Drive.
Allow the engine to idle for 5 minutes.
Shift the transmission into Park.
Allow the engine to idle for 5 minutes.
Turn OFF the engine for 30 seconds.
Manual Transmission
Turn OFF the ignition.
Restore the PCM battery feed.
Turn OFF the A/C controls.
Set the parking brake and block the drive wheels.
Place the transmission in Neutral.
Start the engine.
Ensure that the engine coolant temperature is more than 80°C (176°F).
Allow the engine to idle for 5 minutes.
Turn OFF the engine for 30 seconds.
[Modified by chuckster, 9:46 PM 9/19/2002]
[Modified by chuckster, 9:49 PM 9/19/2002]
In the past I have said that my car pops and bangs loudly upon decelaration. And it did that until tonight...
2 nights ago I did a read of my PCM with LS1-Edit. Also during the read all my valet lights came on by themselves and stayed on till I turned the key off. Anyway, I did not drive the car after that . I finally had the chance to take it out tonight.
As I pull down the driveway it started sounding really wierd at the exhaust. Almost like is was missing and chugging... then it went away....and a few seconds later I got a check engine light. ( Later I checked it and it was P1518 TAC Module)
Anyway I started wondering what was happening and it dawned on me that the PCM was relearning. The P1518 Code must have set when I did not let the PCM do an Idle learn. I drove away right after starting it.
Anyway after I got back after driving about 20 miles...The popping on Decelaration was all but gone....This is weird!
I got this Info from Ken at Carputing. He said anytime the PCM is read or written to it forces a relearn.
So this got me to thinking...If the PCM is relearning, is it also relearning the idle too? Was that bad that I just pulled away? What is protocol here? How about guys who Dyno tume and upload changes after every run? Don't they have to let the PCM stabilize? Please somebody explain..
:confused: :confused: :confused:
I saw this too. It specifically states if the PCM has been written to an Idle LEarn must be done. But with LS1-Edit I guess a read causes the same condition.
Idle Learn Procedure
Idle Learn Procedure
Anytime the powertrain control module (PCM) or the battery is disconnected, the PCM loses power, or the PCM is reprogrammed, the PCMs learned idle position is lost. The engine idle is unstable when the learned idle position is lost.
Perform the following procedure in order to return the learned idle to the correct position:
Automatic Transmission
Turn OFF the ignition.
Restore the PCM battery feed.
Turn OFF the A/C controls.
Set the parking brake and block the drive wheels.
Start the engine.
Ensure that the engine coolant temperature is more than 80°C (176°F).
Shift the transmission into Drive.
Allow the engine to idle for 5 minutes.
Shift the transmission into Park.
Allow the engine to idle for 5 minutes.
Turn OFF the engine for 30 seconds.
Manual Transmission
Turn OFF the ignition.
Restore the PCM battery feed.
Turn OFF the A/C controls.
Set the parking brake and block the drive wheels.
Place the transmission in Neutral.
Start the engine.
Ensure that the engine coolant temperature is more than 80°C (176°F).
Allow the engine to idle for 5 minutes.
Turn OFF the engine for 30 seconds.
[Modified by chuckster, 9:46 PM 9/19/2002]
[Modified by chuckster, 9:49 PM 9/19/2002]
09-20-2002, 12:42 AM
#2
Drifting
Re: PCM Relearns After any Read or Write to the PCM. LS1-Edit Strange behavior. (Buckmaster)
P1518 has nothing to do with you just driving away, see my other response.
Your lights were acting up because the bcm got confused during the pcm read (excess bus activity). I had this the first time I read my pcm, just unhook the battery for a couple seconds and reconnect it. All devices will reboot and resync.
As far as idle relearn. Sometimes I dont even bother.
Eric
Your lights were acting up because the bcm got confused during the pcm read (excess bus activity). I had this the first time I read my pcm, just unhook the battery for a couple seconds and reconnect it. All devices will reboot and resync.
As far as idle relearn. Sometimes I dont even bother.
Eric
09-20-2002, 09:43 AM
#3
Safety Car
Member Since: Aug 2000
Location: Murphy TX
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Cruise-In II Veteran
Re: PCM Relearns After any Read or Write to the PCM. LS1-Edit Strange behavior. (chuckster)
The term "relearn" though commonly used is not really accurate. The system is actually continuously adaptive, i.e. it is (almost) always "learning."
You are correct that flashing while on the dyno poses some interesting questions. There's a Heisenberg issue here. ;) You really want something like EFILive Pro's real time editing capabilities for that kind of tuning. That said, I haven't looked at it closely enough to know whether it has everything you'd want to manipulate.
You might get more response in the new C5 Scan & Tune forum.
You are correct that flashing while on the dyno poses some interesting questions. There's a Heisenberg issue here. ;) You really want something like EFILive Pro's real time editing capabilities for that kind of tuning. That said, I haven't looked at it closely enough to know whether it has everything you'd want to manipulate.
You might get more response in the new C5 Scan & Tune forum.