GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2005 🢒 L300/LW300 🢒 DTC 🢒 DTC P0731

Circuit Description

The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input shaft speed sensor (ISS) and the vehicle speed sensor (VSS). The TCM compares the known transmission gear ratio to a calculated ratio for each commanded gear.

If the TCM detects an incorrect 1st gear ratio, indicating excessive slip or drag within the transmission, DTC P0731 sets. DTC P0731 is a type C DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0731 Incorrect 1st Gear Ratio

Conditions for Running the DTC
    • No MAF DTCs P0101, P0102, or P0103.
    • No MAP DTCs P0107 or P0108.
    • No TP DTCs P0121, P0122, or P0123.
    • No VSS DTCs P0502 or P0503.
    • No ISS DTCs P0716 or P0717.
    • No transmission fluid pressure (TFP) manual valve position switch DTC P1810.
    • The engine run time is greater than 5 seconds.
    • The TFP manual valve position switch is not indicating PARK or NEUTRAL.
    • The transmission fluid temperature (TFT) is 20-130°C (68-266°F).
    • The TP angle is greater than 15 percent.
    • The vehicle speed is 8 km/h (5 mph) or greater.
    • The time since the last range change is 6 seconds.

Conditions for Setting the DTC

The TCM commands 1st gear and one of the following conditions occurs for 5 seconds:

    • The gear ratio is greater than 7.90:1.
    • The gear ratio is 2.23:1 to 2.87:1.
    • The gear ratio is 1.71:1 to 2.02:1.
    • The gear ratio is 1.07:1 to 1.54:1.
    • The gear ratio is 0.71:1 to 0.91:1.
    • The gear ratio is less than 0.60:1.

Action Taken When the DTC Sets
    • The TCM does not request the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
    • The TCM requests the ECM to illuminate the service vehicle soon (SVS) lamp.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
    • The TCM stores DTC P0731 in TCM history.

Conditions for Clearing the SVS Lamp/DTC
    • The TCM clears the SVS lamp request when the condition no longer exists.
    • A scan tool can clear the SVS Lamp/DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the fault no longer exists and the DTC passes.

Diagnostic Aids
    • Ask the customer about overloading the vehicle, exceeding the trailer towing limit, or towing in Overdrive.
    • Inspect for intermittent automatic transmission ISS circuit conditions.
    • Inspect for intermittent VSS circuit conditions.
    • Ensure that the current calibration is correct for the final drive ratio.
    • Refer to Range Reference .

Test Description

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

  1. This step tests for low fluid level, which may cause slipping, and result in an incorrect gear ratio.

    2.

  2. This step verifies that the correct 1st gear ratio occurs for commanded 1st gear.

    3.

  3. This step tests for low line pressure.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Visually inspect the transmission cooling system for fluid leaks.
  2. Repair leaks as necessary.

Refer to Fluid Leak Diagnosis .

Did you find and correct a condition?

--

Go to Step 8

Go to Step 3

3

Did you perform the Transmission Fluid Checking Procedure?

--

Go to Step 4

Go to Transmission Fluid Check

4

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. 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 TCM.

  3. Record the DTC Failure Records.
  4. Clear the DTC.
  5. Use the scan tool snapshot mode in order to record commanded gear and gear ratio.
  6. Drive the vehicle in D1 and record the 1st gear ratio.

Is the 1st gear ratio within the specified parameters?

2.87:1-3.13:1

Go to Diagnostic Aids

Go to Step 5

5

Did you perform the Line Pressure Check Procedure?

--

Go to Step 6

Go to Line Pressure Check

6
  1. Inspect for the following conditions:
    2. • The forward clutch plates for:
       - Slipping
       - Dragging
       - Being damaged
       - Refer to Clutch Plate Diagnosis .
    • The forward clutch assembly for:
       - Piston and seal assembly (607) for binding, being cracked or leaking
       - Inner seal (608) for plugged orifice
       - Snap rings (600, 605) out of position
       - Housing (609) cracked or plugged feed hole
       - Housing retainer and ball assembly missing or out of position
       - Return spring (606) binding
    • Forward clutch support (114) for:
       - Porosity
       - Leaking
       - Damaged seal rings
       - Plugged feed holes
    • The input sprag (515) damaged or not holding
  2. Repair any of the above items as necessary.

Did you complete the repair?

--

Go to Step 7

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7
  1. Change the AT fluid and filter.

    2. Refer to Automatic Transmission Fluid Filter and Seal Replacement .

  2. Inspect the AT fluid for correct level.
  3. Add new fluid as necessary.

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

  4. Use the scan tool in order to perform the following:
    5. • Set the oil life monitor to 100%.
    • Clear TAP

Did you complete the above procedures?

--

Go to Step 8

--

8

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • The TFT is 20-130°C (68-266°F).
    • Drive the vehicle in D1 with the TP angle greater than 15% in order to obtain a correct 1st gear ratio for 7 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0731.

Has the test run and passed?

2.87:1-3.13:1

Go to Step 9

Go to Step 2

9

With the scan tool, observe the stored information, capture info. and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK