DTC P1811 Maximum Adapt and Long Shift Diesel Only
| Table 1: | 4L80-E Range Reference, modified for DTCs P1870 & P1871 |
| Table 2: | DTC P1811 Maximum Adapt-Long Shift Time |
Range | Gear | 1-2 Sol | 2-3 Sol | Fourth Clutch | Overrun Clutch | O/D Roller Clutch | FWD Clutch | Direct Clutch | Front Band | Interm. Sprag Clutch | Interm Clutch | Lo Roller Clutch | Rear Band |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Overdrive | 1st | On | Off | -- | -- | H | A | -- | -- | * | -- | H | -- |
2nd | Off | Off | -- | -- | H | A | -- | -- | H | A | O | -- | |
3rd | Off | On | -- | -- | H | A | A | -- | O | A | O | -- | |
4th | On | On | A | -- | O | A | A | -- | O | A | O | -- | |
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Circuit Description
The Powertrain Control Module (PCM) compares the measured gear ratio to the known actual value. This allows the PCM to determine the actual gear range of the transmission. When an upshift is commanded, the PCM measures the interval during which the gear ratio leaves the current range and changes to reflect the commanded upshift. This interval is expressed on the scan tool as Shift Time. When this interval has exceeded a predetermined limit, the PCM utilizes the shift adapts in order to attempt to shorten the shift time.
If the PCM detects that the maximum allowable shift time has been exceeded, and that the upshift adapts have reached their upper limit, then DTC P1811 sets. DTC P1811 is a type D DTC.
Conditions for Setting the DTC
| • | The engine must be running at greater than 475 RPM for more than 7 seconds. |
| • | One of the following conditions exists, with the adapt cells at the maximum pressure allowed for 5 consecutive occurrences of one shift. |
| - | The 1-2 or the 2-3 upshifts are greater than 1.25 seconds. |
| - | The 3-4 upshifts are greater than 6.37 seconds. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | The PCM freezes shift adapts. |
| • | The PCM commands maximum line pressure. |
| • | DTC P1811 is stored in PCM history. |
Conditions for Clearing the DTC
| • | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | DTC P1811 can be caused by a faulty turbocharger or wastegate assembly. If no other symptoms are present, check the turbocharger system for proper operation. |
| • | Ask the customer about overloading the vehicle, exceeding the trailer-towing limit, or towing in Overdrive. |
| • | If, after several unsuccessful attempts to gain accurate shift times, and an adapt can be made, reset adapts and operate the vehicle, in order to assure proper shifting. |
| • | While driving the vehicle, inspect for loss of power, misfire, or other engine-related driving problems. |
Test Description
-
This step tests for low fluid level, which can cause delayed shifts.
-
This step compares the indicated range signal from the Range Signal table to the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) selected gear range.
-
This step tests for low line pressure, which can cause delayed and long shifts.
Step | Action | Value(s) | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||||
Have you performed the transmission fluid checking procedure? | -- | Go to Transmission Fluid Check | ||||||||||||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM. Important: If any other engine or transmission DTCs are set, refer to their respective diagnostic tables first. Does each selected transmission range match the TFP Sw. A/B/C display on the scan tool? (Refer to the Range Signal table.) | -- | |||||||||||||||||
4 |
Were all of the shift times greater than the specified value? | 1-2 or 2-3 upshifts: 1.25 seconds 3-4 upshifts: 6.37 seconds. | ||||||||||||||||
Perform the line pressure test. Refer to Line Pressure Check . Is the line pressure within specifications? | -- | Go to Symptom Diagnosis table, Low Line Pressure | ||||||||||||||||
6 |
Refer to Changing the Fluid and Filter, in On-Vehicle Service. Is there excessive contamination in the transmission oil pan? | -- | Go to Transmission Overhaul Procedure, in Unit Repair. | |||||||||||||||
7 | Inspect the transmission for fluid pressure loss in one of the following areas:
Refer to Transmission Overhaul Procedure, in Unit Repair. Did you find and correct the condition? | -- | -- | |||||||||||||||
8 | Select the 1-2, 2-3, and the 3-4 Transmission Adaptive Pressure (TAP) cells on the scan tool. Were any of the upshift TAP cells greater than the specified value? | 16.0 PSI | Go to Diagnostic Aids | |||||||||||||||
9 | Did the 3-4 shift time exceed the specified value? | 6.37 seconds | ||||||||||||||||
10 | Did the 2-3 shift time exceed the specified value? | 1.25 seconds | ||||||||||||||||
11 | Did the 1-2 shift time exceed the specified value? | 1.25 seconds | -- | |||||||||||||||
12 | Inspect the following 3-4 shift circuit components:
Refer to Transmission Overhaul Procedure, in Unit Repair. Did you find and correct the condition? | -- | -- | |||||||||||||||
13 | Inspect the following 2-3 shift circuit components:
Refer to Transmission Overhaul Procedure, in Unit Repair. Did you find and correct the condition? | -- | -- | |||||||||||||||
14 | Inspect the following 1-2 shift circuit components:
Refer to Transmission Overhaul Procedure, in Unit Repair. Did you find and correct the condition? | -- | -- | |||||||||||||||
15 | In order to verify your repair, perform the following procedure:
Are the 1-2, 2-3, or 3-4 shift times less than the specified value? | 1-2 and 2-3 upshifts 1.25 seconds 3-4 upshifts 6.37 seconds | System OK |
