P0731

DTC P0731

Diagnostic Instructions
^ Perform the [Diagnostic System Check - Vehicle Diagnostic Information] prior to using this diagnostic procedure.
^ Review [Strategy Based Diagnosis] for an overview of the diagnostic approach. Strategy Based Diagnosis
^ [Diagnostic Procedure Instructions - Vehicle Diagnostic Information] provides an overview of each diagnostic category. Diagnostic Procedure Instructions - Vehicle Diagnostic Information

DTC Descriptor
DTC P0731 Incorrect 1st Gear Ratio

Circuit/System Description
The transmission control module (TCM) calculates the actual gear ratio based on input speed sensor (ISS) and output speed sensor (OSS) data. The actual gear ratio is compared to the expected gear ratio for each commanded gear. If the TCM detects an incorrect 1st gear ratio while in 1st gear, DTC P0731 sets.

Conditions for Running the DTC
^ No Throttle Position (TP) Sensor DTC P0120.
^ No Transmission Range (TR) Switch DTCs P0706, P0707, or P0708.
^ No Transmission Fluid Temperature (TFT) Sensor DTCs P0711, P0712, or P0713.
^ No Speed Sensor DTCs P0717, P0722, or P0727.
^ No Pressure Control (PC) Solenoid DTCs P0962, P0963, P0966, P0967, P0970, or P0971.
^ No Shift Solenoid (SS) Control Circuit DTCs P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0983, P0985, or P0986.
^ No Transmission Torque Delivered Circuit DTC P2637.
^ No Communications DTCs U0100 or U2104.
^ Output speed greater than one half that of the input speed.
^ Input speed is greater than 400 RPM.
^ Current gear equals 1st for at least 8 seconds.
^ Transmission fluid temperature (TFT) is greater than 20°C (68°F).
^ Engine speed is greater than 400 RPM.
^ Engine speed is greater than the input speed plus 150 RPM for 0.5 second.
^ Engine torque is 30-200 Nm (22-148 ft. lbs.).
^ Input torque fluctuation is less than 25 Nm (18 ft. lbs.).
^ Shift range equals D, M, or L.
^ Ignition voltage is greater than 10.5 volts.

Conditions for Setting the DTC
The following condition is met for 1 second, 5 occurrences. Input speed - 4.657 times the output speed is greater than 300 RPM and Input speed - 2.301 times the output speed is less than 100 RPM.

Action Taken When the DTC Sets
^ DTC P0731 is a Type A DTC.
^ Inhibit 1st gear.
^ No control during N to D garage shift.

Conditions for Clearing the DTC
DTC P0731 is a Type A DTC.

Diagnostic Aids
Improper transmission fluid level may cause DTC P0731 to set.

Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool.
2. Record Freeze Frame and Failure Records.
3. Clear DTCs.
4. Operate the vehicle under the conditions observed in the Failure Records.
5. Observe the DTC information with the scan tool. Verify that the DTC does not set.

Circuit/System Testing
1. Operate the vehicle in 2nd gear. The engine should not stall when shifting into 2nd gear.
> Inspect and repair as necessary, the control valve body assembly for a stuck 3-4, 4-5 solenoid valve or a stuck U1 shift valve.
2. Observe the scan tool Transmission OSS parameter. The reading should correspond to a known properly functioning OSS.
> If the OSS is malfunctioning, replace the Transmission Output Speed Sensor (OSS).
3. Stop the vehicle, apply the parking brake, engine at idle, select P (park) using the Shift Control.
4. Observe the scan tool Transmission ISS parameter. The reading should be within 400-800 RPM.
> If the ISS parameter is not within the specified range, replace the Transmission Input Speed Sensor (ISS).
5. Firmly apply the brake, select D (drive) using the Shift Control.
6. Observe the scan tool TCC Slip Speed. The reading should be within 0-100 RPM.
> If the TCC Slip Speed is not within the specified range:
^ Ignition ON, engine OFF, command shift solenoid 1 ON and OFF with a scan tool. The solenoid should click when commanded ON.
> If the solenoid does not click, replace the 1st shift solenoid valve assembly.
^ Command shift solenoid 3 ON and OFF with a scan tool. The solenoid should click when commanded ON.
> If the solenoid does not click, replace the 1-2, 2-3, reverse shift solenoid valve assembly.
^ Perform a line pressure test.
^ Remove the control valve body cover.
^ Inspect the inside of the control valve body cover for excessive sediment. There should not be excessive sediment.
> If excessive sediment is found inspect and replace as necessary the low clutch sprag, forward clutch, and 1-2, reverse clutch.
^ Inspect the control valve body assembly for the following conditions. The conditions should not be found.
- Stuck U1 shift valve
- Stuck M1 shift valve
- Stuck U2 shift valve
- Stuck line pressure control solenoid valve assembly
- Stuck neutral relay valve
> If any of the above conditions are found, replace the valve body assembly.
^ Verify that the control valve body has been serviced within the past 3 months.
> If the control valve body has not been serviced, replace the control valve body assembly.
^ If all circuits and components test normal, replace the transmission.
7. If all circuits and components test normal, replace the transmission.

Repair Instructions
Perform the [Diagnostic Repair Verification - Vehicle Diagnostic Information] after completing the diagnostic procedure.