DTC P1811. GMC Truck Savana 2001

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2001 🢒 Savana 🢒 DTC 🢒 DTC P1811

DTC P1811 Diesel Only

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 C DTC.

Conditions for Running the DTC

The engine must be running at greater than 475 RPM for more than 7 seconds.

Conditions for Setting the DTC

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.

•	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 clears the DTC from PCM history.

•	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 fault no longer exists and the ignition switch 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 conditions.

•	Refer to Range Reference .

•	DTC P1811 defaults to an elevated line pressure condition which may result in TCC partial apply. This may induce idle surge and engine stall.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This step tests for low fluid level, which can cause delayed shifts.

This step compares the indicated range signal from the Transmission Fluid Pressure Manual Valve Position Switch Logic table to the automatic transmission fluid pressure (TFP) manual valve position switch selected gear range.

This step tests for low line pressure, which can cause delayed and long shifts.

DTC P1811 Maximum Adapt-Long Shift Time

Step

Action

Value(s)

Yes

Did you perform the Powertrain Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls

Perform the Transmission Fluid Checking Procedure.

Refer to Transmission Fluid Check .

Was the Transmission Fluid Checking Procedure performed?

Go to Step 3

Go to Transmission Fluid Check

Install a Scan Tool .
Turn ON the ignition, with the engine OFF.

Important: Before clearing the DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the PCM.

Record the DTC Failure Records.
Clear the DTC.

Important: If any other engine or transmission DTCs are set, refer to their respective diagnostic tables first.

Select TFP Sw. A/B/C on the Scan Tool .
Start the engine and apply the brake pedal.
Select each gear range: D1, D2, D3, D4, N, R, and P.

Refer to Transmission Fluid Pressure Manual Valve Position Switch Logic .

Does each selected transmission range match the TFP Sw. A/B/C display on the Scan Tool ?

Go to Step 4

Go to DTC P1810

Drive the vehicle in D4 in order to obtain a 1-2, a 2-3, and a 3-4 shift time. Use the Scan Tool snapshot mode in order to record the shift times.
Use the Scan Tool to review the shift time information for 1-2, 2-3, and 3-4 shift times.

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

Go to Step 5

Go to Step 8

Perform the Line Pressure Check Procedure.

Refer to Line Pressure Check .

Is the line pressure within specifications?

Go to Step 6

Go to Symptoms - Automatic Transmission

Remove the transmission oil pan.

Refer to Automatic Transmission Fluid and Filter Replacement .

Inspect the pan and the fluid for contamination.

Is there excessive contamination in the transmission oil pan?

Go to Transmission Overhaul in Transmission Unit Repair Manual

Go to Step 7

Inspect the transmission for fluid pressure loss in one of the following areas:

•	Valve body gasket

•	Forward clutch seals

•	Turbine shaft seals

Refer to Transmission Overhaul in Transmission Unit Repair Manual.

Did you find and correct the condition?

Go to Step 15

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 psi (110 kPa)

Go to Step 9

Go to Diagnostic Aids

Did the 3-4 shift time exceed the specified value?

6.37 seconds

Go to Step 12

Go to Step 10

Did the 2-3 shift time exceed the specified value?

1.25 seconds

Go to Step 13

Go to Step 11

Did the 1-2 shift time exceed the specified value?

1.25 seconds

Go to Step 14

Inspect the following 3-4 shift circuit components:

•	4th gear clutch plates

•	4th gear clutch seals

•	A sticking 3-4 shift valve

Refer to Transmission Overhaul in Transmission Unit Repair Manual.

Did you find and correct the condition?

Go to Step 15

Inspect the following 2-3 shift circuit components:

•	Turbine shaft seals

•	Forward clutch plates

•	Forward clutch seals

•	Direct clutch plates

•	Direct clutch seals

•	Center support seals

•	Improperly tightened center support bolt

Refer to Transmission Overhaul in Transmission Unit Repair Manual.

Did you find and correct the condition?

Go to Step 15

Inspect the following 1-2 shift circuit components:

•	Low roller clutch

•	Intermediate clutch plates

•	Intermediate clutch seals

•	Intermediate sprag clutch

•	Overdrive roller clutch

•	Improperly tightened center support bolt

Refer to Transmission Overhaul in Transmission Unit Repair Manual.

Did you find and correct the condition?

Go to Step 15

Change the AT fluid and filter.
Inspect for correct transmission fluid level.

Refer to Transmission Fluid Check .

Add new AT fluid as necessary.

Important: The Clear TAPS function will clear all adapt cells. This may affect transmission performance. The PCM will update the transmission adapt cell values as the vehicle is driven.

Use the Scan Tool to perform the Clear TAPS function.

Did you complete the above procedure?

Go to Step 16

Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Drive the vehicle in D4 range.
Operate the vehicle through several 1, 2, 3, 4 upshifts.
Review the Scan Tool 1-2, 2-3 and 3-4 shift times.

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

Go to Step 1