issues after disconnecting battery? [Archive] - GrandAmGT.com Forum

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Metalxen
07-02-2012, 11:29 PM
I've searched just about everywhere for an answer on this,but can't find what I'm looking for. So any help on this would really be appreciated. I just installed an ipod interface unit on the stock deck a couple of days ago,followed the instructions without any snags. Reconnected the battery, fired up the car, all is good, tunes sound awesome. So I take her out for a little test drive,and now the trans is not hitting the shifts like it's supposed to.I had problems like this before that were linked to a dirty maf sensor. I pulled the sensor out and cleaned it, seems a little better but the trans still lags a bit. I also pulled that ipod interface back out again thinking that it may be the problem but the lag is still there. Now I think I read somewhere on here that if the battery gets disconnected it will take some time for the (tuned) pcm to correct the trans lag. Is this true, and how long will this take? Never had any issues until I messed with the stereo.

HOYS
07-03-2012, 12:24 AM
Copypasta about a "similar" transmission and what the learning function is:

Transmission Adaptive Functions

The 4L60-E transmission utilizes a line pressure control system during upshifts to compensate for the normal wear of transmission components. By adjusting the line pressure, the PCM can maintain acceptable transmission shift times. This process is known as "adaptive learning" or "shift adapts" and is similar to the closed loop fuel control system used for the engine.

In order for the powertrain control module (PCM) to perform a "shift adapt," it must first identify if an upshift is acceptable to analyze. For example, upshifts that occur during cycling of the A/C compressor or under extreme throttle changes could cause the PCM to incorrectly adjust line pressure. When an upshift is initiated, a number of contingencies, such as throttle position, transmission temperature, and vehicle speed, are checked in order to determine if the actual shift time is valid to compare to a calibrated desired shift time. If all the contingencies are met during the entire shift, then the shift is considered valid and the adapt function may be utilized if necessary.

Once an adaptable shift is identified, the PCM compares the actual shift time to the desired shift time and calculates the difference between them. This difference is known as the shift error. The actual shift time is determined from the time that the PCM commands the shift to the start of the engine RPM drop initiated by the shift. If the actual shift time is longer than the calibrated desired shift time, a soft feel or slow engagement, then the PCM decreases current to the pressure control (PC) solenoid in order to increase line pressure for the next, same, upshift under identical conditions. If the actual shift time is shorter than the calibrated desired shift time, a firm engagement, then the PCM increases current to the PC solenoid in order to decrease line pressure for the next, same, upshift under identical conditions.

The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. It is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle.

Clearing Transmission Adaptive Pressure (TAP)
Transmission adaptive pressure (TAP) information is displayed and may be reset using a scan tool.

The adapt function is a feature of the PCM that either adds or subtracts line pressure from a calibrated base line pressure in order to compensate for normal transmission wear. The TAP information is divided into 13 units, called cells. The cells are numbered 4 through 14. Each cell represents a given torque range. TAP cell 4 is the lowest adaptable torque range and TAP cell 14 is the highest adaptable torque range. It is normal for TAP cell values to display zero or negative numbers. This indicates that the PCM has adjusted line pressure at or below the calibrated base line pressure.

Updating TAP information is a learning function of the PCM designed to maintain acceptable shift times.
It is not recommended that TAP information be reset unless one of the following repairs has been made:
Transmission overhaul or replacement
Repair or replacement of an apply or release component, clutch, band, piston, servo
Repair or replacement of a component or assembly which directly affects line pressure

Resetting the TAP values using a scan tool will erase all learned values in all cells. As a result, the PCM will need to relearn TAP values. Transmission performance may be affected as new TAPs are learned. Learning can only take place when the PCM has determined that an acceptable shift has occurred. The PCM must also relearn TAP values if it is replaced.

Metalxen
07-03-2012, 10:30 PM
Thanks HOYS,interesting read. I assume by disconnecting the battery the T.A.P values were reset and now it's going through a relearn. Strange because I had the battery replaced about two months ago and the trans never acted up then.

Metalxen
07-03-2012, 10:46 PM
Oh yeah, after driving or rather "limping" around today I did notice the shifts were starting to firm up again.:thumbs:

AaronGTR
07-04-2012, 07:44 AM
Thanks HOYS,interesting read. I assume by disconnecting the battery the T.A.P values were reset and now it's going through a relearn. Strange because I had the battery replaced about two months ago and the trans never acted up then.


That is incorrect. Disconnecting power from the battery will only reset the fuel trims. If your O2 sensor is good, it will only take the PCM 15-30 minutes to relearn the fuel trims, and unless your fueling is way off, you won't notice much difference in the way it drives. It also wouldn't have any affect on transmission function. The only thing that affects that are sensors that the PCM uses to calculate engine load, such as MAF, MAP, TPS, etc... O2 sensor is not one of them.

The ONLY way to reset the Trans adaptive learn feature is to do a full flash rewrite of the PCM. The ipod interface wouldn't have anything to do with how the trans is shifting either. It has nothing to do with the power train functions. Sorry to say this, but the problem is either imagined, or due to something else totally unrelated.

shiwnath
07-04-2012, 07:55 AM
That is incorrect. Disconnecting power from the battery will only reset the fuel trims. If your O2 sensor is good, it will only take the PCM 15-30 minutes to relearn the fuel trims, and unless your fueling is way off, you won't notice much difference in the way it drives. It also wouldn't have any affect on transmission function. The only thing that affects that are sensors that the PCM uses to calculate engine load, such as MAF, MAP, TPS, etc... O2 sensor is not one of them.

The ONLY way to reset the Trans adaptive learn feature is to do a full flash rewrite of the PCM. The ipod interface wouldn't have anything to do with how the trans is shifting either. It has nothing to do with the power train functions. Sorry to say this, but the problem is either imagined, or due to something else totally unrelated.

I'm not an expert on the subject, but since I've had my PCM tuned, I had my tuner increase the line pressure. At WOT you can really feel it kick, but after doing a battery reset, at WOT the shifts feel soft and it's a weak shift. After a few days of driving, some sort of "relearn" happens that causes it to shift as it used to... like I said I'm not an expert but that's my experience with this whole matter.

[ChaosweaveR]
07-04-2012, 08:11 AM
My GAGT acted the same way when the battery died last year. The shifts were really sloppy and slow when I first installed the battery. After driving about 35 miles purposely in stop and go traffic and such, the shifts finally firmed up.

AaronGTR
07-04-2012, 11:05 AM
And does anyone have any scan data to support this? Or only seat of the pants "feelings"?


Like I said, it does NOTHING with the transmission. Only fuel trims. Any change in how the engine feels can only be attributed to that. I have the entire article on TAPS on my computer, as well as the factory service manual, and plenty of threads on the tuning forum supported that. TAPS does NOT get reset by disconnecting the battery. It has to be flashed over, and not by a partial flash either. You have to do a full write to overwrite the section where that data is stored. It is not stored in temporary memory.

HOYS
07-04-2012, 11:20 AM
Flashing a calibration in HPT makes the TAPS system reset, and if you have any check engine lights on, they go away, the same thing happens when you leave the battery out for a good bit of time. The capacitors and what not don't store the "short term" memory of the PCM and they get lost, and the computer's settings (past data "written" to the PCM) get reset.

[ChaosweaveR]
07-04-2012, 11:20 AM
Then what would cause the trans to "slip" into gear after being reset?

shiwnath
07-04-2012, 12:30 PM
And does anyone have any scan data to support this? Or only seat of the pants "feelings"?


Like I said, it does NOTHING with the transmission. Only fuel trims. Any change in how the engine feels can only be attributed to that. I have the entire article on TAPS on my computer, as well as the factory service manual, and plenty of threads on the tuning forum supported that. TAPS does NOT get reset by disconnecting the battery. It has to be flashed over, and not by a partial flash either. You have to do a full write to overwrite the section where that data is stored. It is not stored in temporary memory.

Well sir, according this article it appears TAPS can be reset by disconnecting the battery. BUT there are two issues with the article. 1. it was written about the 4t60 trannys and 2. Not sure if this source is credible. I would assume that the 4T60 and 4T40s would operate in a similar fasion when it comes to reset procedures.
http://www.sonnax.com/system/pdfs/135/original/TASC-TIP-05-05.pdf?1289926276

I'm not gonna sit here and argue about whether or not TAPS resets after the battery is pulled because I have no actual proof. All I can say is, after driving my car for thousands of Ks, I know how it acts and feels. After pulling the battery, yes my car shifts kinda spongy. Whether it's from TAPS or something else, that is the question.

AaronGTR
07-04-2012, 02:01 PM
Flashing a calibration in HPT makes the TAPS system reset, and if you have any check engine lights on, they go away, the same thing happens when you leave the battery out for a good bit of time. The capacitors and what not don't store the "short term" memory of the PCM and they get lost, and the computer's settings (past data "written" to the PCM) get reset.


Flashing the PCM with DHP does the same thing with DTC's and fuel trims, but I was under the impression that TAPS data was not stored in the short term memory because I was told that doing a partial write would not reset this, and that a full write had to be done to change the block where that data was stored. It's possible they were wrong, or maybe they were talking about the data for the function of the TAPS, and not the learned TAPS settings themselves. No idea.


Well sir, according this article it appears TAPS can be reset by disconnecting the battery. BUT there are two issues with the article. 1. it was written about the 4t60 trannys and 2. Not sure if this source is credible. I would assume that the 4T60 and 4T40s would operate in a similar fasion when it comes to reset procedures.
http://www.sonnax.com/system/pdfs/135/original/TASC-TIP-05-05.pdf?1289926276

I'm not gonna sit here and argue about whether or not TAPS resets after the battery is pulled because I have no actual proof. All I can say is, after driving my car for thousands of Ks, I know how it acts and feels. After pulling the battery, yes my car shifts kinda spongy. Whether it's from TAPS or something else, that is the question.


I have the same article. Been a while since I read it. I don't recall 100%, but I don't believe our scanners have the ability to read the TAPS data cells like the screen shots in that article, so I was never able to make much use of it. Same way as our tuners are not able to reset the TAPS separately like it can the fuel trim. You would need a Tech2 or similar for that.

But anyway, the issue most people were having back in the day was not with shifts going soft after resetting like you are saying, but rather their shifts were getting soft over time and they were having to reset TAPS to firm them up again. Granted these people had tuned their PCM for harder shifts than factory settings, and some of them had built transmissions. It's entirely possible though that they didn't have them tuned properly. If they increased line pressures but didn't decrease the corresponding desired shift times (or missed some other setting) the PCM may have seen to short a shift time from the increased base pressure and TAPS might have decreased the pressure accordingly to achieve the programmed shift time.

You may have the opposite problem. If your trans is stock and your clutches are worn, TAPS might be increasing pressure, and when reset (how ever that is accomplished) your shifts will get soft. So maybe you need to increase your base desired shift pressure and (possibly) adjust the shift times? That might prevent your shifts from going soft whenever your PCM is reset. You'll just have to experiment and find out. Unfortunately there isn't a lot of reliable info out there on it, and a lot of people who used to tune these cars (and the GP's) have moved on.

Metalxen
07-04-2012, 08:36 PM
Well there has to be something related to the battery being disconnected that caused the trans to suddenly start lagging. I know I'm not imagineing things, I had no issues at all before doing so.It was as if someone flicked a switch, and now the dam thing seems to be correcting itself.The reason why I mentioned the ipod was because I thought I may have grounded to something I should'nt have, but that turned out to not be the case. The only code the car has ever had and still has is p0420 post cat 02 sensor and it's been there for 6 years now.

[ChaosweaveR]
07-04-2012, 08:50 PM
Seriously...what LA1 powered GA DOESN'T have that code issue? lol

Metalxen
07-04-2012, 09:15 PM
;1182083']Seriously...what LA1 powered GA DOESN'T have that code issue? lol yeah, I'm too lazy to put the 02 sim on :D

AaronGTR
07-04-2012, 11:37 PM
Have you ever changed the cat? My car has never had that code.

Metalxen
07-08-2012, 01:31 AM
Have you ever changed the cat? My car has never had that code.
I went with the 2.5" down pipe back exhaust system with high flow cat (I was planning on installing headers at some point but never got around to it).So I think thats why the
efficiency code showed up. Then again I never did bother to change the sensor either because I've heard so many others had changed them out only to have the code come back again....On a side note the trans is shifting just like it should be now and not like the lagging 2 to almost 3 second shifts it was making earlier this week.Soooo annoying..... I was looking at an 02 simulator on ZZP's web site but it only lists up to the 03 model so I'm not sure if it's compatable for my 05

AaronGTR
07-08-2012, 09:40 AM
It should be, they are all the same.