The transmission pressure is modified by an adaptive modifier which controls the shift execution time. This test checks 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(this causes harsh shifts).
* 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 consecutive warm-up cycles without a non-emission-related diagnostic fault occurring.
* The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.
* Ask the customer about possible overloading, exceeding the trailer towing limit, or towing in overdrive.
* Ensure that the PCM has the latest calibration update.
Basically what it is saying is that the powertrain control module (PCM or brainbox) monitors the time it takes for the transaxle to go into a certain gear when it commands that gear electronically with the 1-2 and 3-4 shift solenoids. As the clutches and bands wear in the transmission some slippage occurs and longer shifts take place. The PSC (pressure control solenoid) is used to control line pressure in the transaxle for shift quality. The PCM is able to monitor the time and increase line pressure with the EPC or PCS to bring the shift time into limits. In this way the PCM is able to compensate for wear of the transaxle. The PCM adapts to longer shift times by increasing pressure. If the time it takes to shift into a gear exceeds the capability of the PCM to adapt to it, it sets the trouble code P1811. The PCM also commands the PCS so that the transmission has full line pressure. Under full line pressure the transmission will shift hard to protect the clutches and bands from slipping.
Whatever you do, don't clear the trouble code. If you do, you will lose the freeze frame record when the P1811 set. When a trouble code is set the PCM takes a snap shot of all the data. This helps the technician to determine why the code may have set. The shift times are recored, so the technician can look at those times and see if the 1-2 or 3-4 or both exceeded time limits. Knowing which shift exceeded the limit will help the technician to pinpoint the area of the transaxle to diagnose and repair.
P1811 is a generic overview of the shift adapts failing to compensate for exceeded shift times. It doesn't necessarily mean that the EPC or PCS is the blame for the problem.
For example: If the failure records showed 1-2 shift times where exceeded, these are the possible culprits:
Inspect the transmission for the following conditions:
* 1-2 accumulator piston seals rolled or damaged
* 1-2 accumulator piston and pin missing, binding or damaged
* Forward servo assembly damaged or misassembled
* Oil pump assembly damaged or missing components
* Spacer plate and gaskets damaged or misassembled
* Driven sprocket support seals damaged or missing
* Second clutch piston and seal assembly binding or damaged
* Second clutch fiber and steel plates misassembled, burned or damaged
* Second clutch spring assembly damaged or misassembled
* Forward band burned, damaged or misassembled
* 1-2 support roller clutch assembly damaged or misassembled