P1811

[mgssrs]

I'm new to this site but have read a lot of good information on here. I have read a lot about the P1811 code and have some questions about it.
I had the trans fluid and filter changed on my 2005 Grand Prix at 96000 mi. The fluid looked and smelled okay before changing. Shortly after we started to notice a slip when starting out from a stop. My wife drives it mostly and thought it was the tires spinning on ice or snow. It only does it once every few days. So I brought it back to the trans shop and they said they notice the slip and pulled the P1811 code. They pulled the pan and filter and found them to be clean but still want to do a complete rebuild.
I don't notice any other hard shifting or the whining that others have talked about with this code. So my questions are.
1 Will the pressure control solenoid cause this slip from a dead stop and not notice the hard shifts in other gears?
2 Is it worth changing the pressure control solenoid without a rebuild?
3 Would the shift kits help at all with the engaging problem at start up?

Thanks for any help on this.

[jdmccright]

I don't know for sure but the PCS can be replaced by just removing the pan to access the solenoids. No reason in my mind for a rebuild...especially at that low mileage. You should be able to test the line pressure and/or access the pressure data from the OBD port.

No, shift kits won't help. These should only be installed onto healthy transmissions.

[mgssrs]

Thanks for the reply.

[BNaylor]

The best thread we have on the P1811 DTC for the GM 4T65E transaxle is at the link below. The PCS is a common problem. However, it requires transaxle knowledge and some experience to replace. Plus the process is tedious and difficult even for a DIY person. Located under the left side cover assembly and not under the bottom pan. See pic. A shift kit can help older higher mileage transaxles but review the responses at the link since there are variables involved.

Click here




EPC- Pressure Control Solenoid (PCS) 4T65E Autotransaxle

[mgssrs]

Thanks BNaylor you seem to be the go to guy on this topic. I am not sure I have the same problem as most others My trans was working fine when I had the fluid and filter changed and I believe flushed. I started to notice a hard engage from a stop like once every day or two. I brought it back to have them check it out and that is when they found the P1811. They cleared it and it has not come back in the week since. I don't notice the hard shift in any other gears or the whining sound only the slip from a stop. Feels like a neutral drop into drive.
It seems to have started from the fluid change. They said the pan looked good with no shaving but they want to rebuild it. I am thinking off doing the seafoam and switch to dexron six. I would guess that the shift kits that you have installed would not help at take off only shifting from 1 to 2 is that what you would say.
Any more advice or info would be very much appreciated.

[ronjoyce]

Here is the only bulletin on the GM site I could find for this code:

Service Information

Document ID: 2323213
#09-07-30-013A: Intermittent Harsh Upshifts or Downshifts, DTC P1811 (Maximum Adapt and Long Shift) (Reprogram TCM) - (Aug 6, 2009)

Subject: Intermittent Harsh Upshifts or Downshifts, DTC P1811 (Maximum Adapt and Long Shift) (Reprogram TCM)
Models: 2005-2008 Buick LaCrosse/Allure
Equipped with 3.6L Engine (RPO LY7) and 4T65 Automatic Transmission (RPO M15)
2007 Buick Terraza
2007-2009 Chevrolet Uplander
2007-2009 Pontiac Montana
2007 Saturn Relay
Equipped with 4T65 Automatic Transmission (RPO M15 or M76)

This bulletin is being revised to change the labor time information. Please discard Corporate Bulletin Number 09-07-30-013 (Section 07 - Transmission/Transaxle).

Condition

Some customers may comment on harsh or firm upshifts or downshifts. These conditions may be intermittent. Diagnosis may indicate that DTC P1811 (Maximum Adapt and Long Shift) has been set. This condition may also include intermittent harsh upshifts at low speeds when lifting out of throttle, and harsh downshifts at 2-1 coast down, or harsh shifts when rolling to a stop and stepping into the throttle before completely stopped.

Cause

These conditions may be caused by the TCM setting a DTC P1811. This may not be observable on the Tech 2®. With a P1811, the SES light is not illuminated, but the transmission defaults to maximum line pressure. While the code is active and at maximum line pressure, all shifts may be harsh including upshifts, downshifts and shifts out of PARK. When the code is not active, most shifts may seem normal. However, the customer may comment on intermittent harsh upshifts and harsh downshifts, and a delay with harsh shifts when rolling to a stop and stepping into throttle before completely stopped.

Correction

An updated TCM calibration has been developed to address this condition. If the Service Information for the conditions described above do not isolate a fault, reprogram the TCM with the latest calibration available. Verify that the multiple diagnostic interface (MDI) that is being used is configured to the PC that will be used.

Important: Confirm the newest calibration includes the following description: "Select this calibration only to address DTC P1811 (Maximum Adapt and Long Shift), Harsh Upshifts, or Downshifts." This calibration should only be used to repair vehicles that have the subject condition. This calibration, or any that follow, is designed to address this concern. Use of this calibration to attempt to fix other conditions will not be successful and are subject to warranty claim review.

Note: Reprogram the TCM with the software now available in the TIS2WEB using the Service Programming System (SPS). If you cannot access the calibration, call the Techline Customer Support Center at 1-800-828-6860 (English) or 1-800-503-3222 (French) and it will be provided. As always, make sure your Tech 2® Diagnostic Scan Tool is updated with the latest software version. Clear any codes and verify the condition has been fixed.

Warranty Information

For vehicles repaired under warranty, use:

Labor Operation

Description

Labor Time

K9535

Transmission Control Module Transmission Reprogramming with SPS

0.4 hr

[mgssrs]

Thanks ronjoyce. That sounds a lot like what I am getting. Do you know if a GM dealer would reprogam it if it is out of warranty? Or would they only do a diagnostic and then recommend a rebuild like Kennedy Trans.

[ronjoyce]

Not that I am aware of. You may want to try a few local service centers and get some estimates. Wish I knew of someone that did it at a reasonable cost. Not sure what the charge would be. Looks like .4 hour but am sure there is a flat fee to start with.