Code P1811, transmission shifting hard

RAY DAWKINS

MEMBER
2002 BUICK CENTURY
3.1L
6 CYL
2WD
AUTOMATIC
109,000 MILES

The transmission shifts hard after reaching normal operation temperature. It shifts fine when it's cool. What causes this code and how can it easily be fixed?

Monday, April 6th, 2020 AT 5:48 AM

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

What code? There is no code number listed. Can you post the code? Got it, sorry.

https://www.2carpros.com/articles/automatic-transmission-problems

How long since you changed the fluid and filter?

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

The description is below and the flow chart is there to follow.

Roy

Circuit Description
The transmission pressure is modified by an adaptive modifier which controls the shift execution time. This diagnostic tests the time required to accomplish the shift. If the shift takes longer than 0.65 seconds and the adaptive modifier cannot shorten this time, then a counter increases by one.
If the PCM detects a counter value of 2 during one trip, then DTC P1811 sets. DTC P1811 is a type C DTC.

Conditions for Running the DTC
The shift is adaptable.
The 1-2, the 2-3 or the 3-4 shift adapt cell has reached its limit.

Conditions for Setting the DTC
The 1-2, 2-3 or 3-4 shift is longer than 0.65 seconds, twice in one trip.

Action Taken When the DTC Sets
The PCM does not illuminate the malfunction indicator lamp (MIL).
The PCM commands maximum line pressure.
The PCM freezes shift adapts.
The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
The PCM stores DTC P1811 in PCM history.

Conditions for Clearing the DTC
A scan tool can clear the DTC.
The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
Ask the customer about possible overloading, exceeding the trailer towing limit, or towing in overdrive.
Ensure that the current PCM calibration is correct for the final drive ratio.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
7. This step inspects components that may cause low line pressure.
9. This step inspects or repairs components that may cause a maximum adapt and long 1-2 upshift.
11. This step inspects or repairs components that may cause a maximum adapt and long 2-3 upshift.
13. This step inspects or repairs components that may cause a maximum adapt and long 3-4 upshift.

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