For 1990-2009 cars

### Circuit Description

The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input shaft speed (AT ISS) and automatic transmission output shaft speed (AT OSS) sensors. The TCM compares the calculated gear ratio to the known gear ratio for each commanded gear.

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

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0731 Incorrect 1st Gear Ratio

### Conditions for Running the DTC

• | No TR switch DTC P0705.

• | No transmission fluid temperature (TFT) DTCs P0711, P0712, or P0713.

• | No ISS DTC P0717.

• | No OSS DTC P0722.

• | No engine speed DTC P0727.

• | No solenoid DTCs P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0983, P0985, or P0986.

• | No engine torque DTC P1781.

• | No throttle position DTC P1791.

• | No controller area network (CAN) DTCs U2104 or U0100.

• | The ignition voltage is 10.5-18 volts.

• | The transmission temperature is greater than 20°C (68°F).

• | Engine torque is between 30-200 N·m (22.13-147.51 lb ft).

• | The transmission is in a forward range.

• | The elapsed time since the most recent range change is 8 seconds or greater.

• | The engine speed is at least 400 RPM and is at least 150 RPM greater than input shaft speed (ISS) for 0.5 seconds.

• | The commanded gear has been 1st for 0.5 seconds or greater.

• | The transmission input shaft speed (ISS) is 400 RPM or greater.

• | The transmission output shaft speed (OSS) is 200 RPM or greater.

### Conditions for Setting the DTC

The TCM commands 1st gear and the actual gear ratio is not within 3.75:1-5.62:1 for 10 seconds.

### Action Taken When the DTC Sets

• | The TCM requests the powertrain control module (PCM) to illuminate the malfunction indicator lamp (MIL).

• | Inhibit 1st gear.

• | The line pressure is at maximum, and freezes the transmission adapt functions.

• | Inhibit garage shift.

• | The PCM records the operating conditions when the Condition for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.

• | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.

• | The TCM stores DTC P0731 in TCM history.

### Conditions for Clearing the MIL/DTC

• | The PCM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.

• | A scan tool can clear the 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 ignition is OFF long enough in order to power down the TCM.

### Diagnostic Aids

Ask the customer about overloading the vehicle, or exceeding the trailer towing limit.

### Test Description

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

1. This step determines that shift solenoid 4 or the U1 shift valve is stuck if the TCC applies in 2nd gear and stalls the engine.

2. This step determines if the output shaft speed sensor signal is skewed by a large factor.

3. This step determines if the input shaft speed sensor signal is skewed by a large factor.

4. This step determines that shift solenoid 2 or the M2 shift valve is stuck if the TCC Slip Speed is near 0 RPM at idle in DRIVE (D).

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Inspect for correct transmission fluid level. Refer to Transmission Fluid Check . Is the transmission fluid level correct? | -- | Go to Step 4 | Go to Step 3
3 |

1. Visually inspect the transmission cooling system for fluid leaks. Refer to Fluid Leak Diagnosis .
2. Repair leaks as necessary.
3. Fill the transmission to the proper fluid level.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 4

4 |

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

Important:

• | Before clearing the DTC, use the scan tool in order to record the PCM and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Failure Records from the powertrain control module (PCM) and the transmission control module (TCM).

• | Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the PCM and 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 DRIVE (D) and record the gear ratio while accelerating in 1st gear.

Is the 1st gear ratio within the specified range?

3.75:1-5.62:1

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 5

5 | Drive the vehicle in 2nd gear. Does the engine stall when the transmission shifts into 2nd gear? | -- | Go to Step 14 | Go to Step 6
6 |

1. Drive the vehicle.
2. Observe Transmission OSS parameter with a scan tool.
3. Compare with a known good vehicle.

Is Transmission OSS parameter reading correctly?

--

Go to Step 7

Go to Step 19

7 |

1. Stop the vehicle and apply the parking brake.
2. Place the gear selector in PARK (P).
3. Allow the engine to idle.
4. Observe Transmission ISS with a scan tool.

Is Transmission input speed sensor (ISS) within the specified range?

400-800 RPM

Go to Step 8

Go to Step 18

8 |

1. Keep the brakes firmly applied.
2. Place the gear selector in DRIVE (D).
3. Allow the engine to idle.
4. Observe TCC Slip Speed parameter with a scan tool.

Is TCC Slip Speed parameter within the specified range?

0-100 RPM

Go to Step 13

Go to Step 9

9 |

1. Turn the ignition ON, with the engine OFF.
2. Command shift solenoid 1 ON and OFF with a scan tool.

Does shift solenoid 1 click when commanded ON?

--

Go to Step 10

Go to Step 20

10 | Command shift solenoid 3 ON and OFF with a scan tool. Does shift solenoid 3 click when commanded ON and OFF? | -- | Go to Step 11 | Go to Step 21
11 | Perform a line pressure test. Refer to Line Pressure Check . Is the action complete? | -- | Go to Step 12 | --
12 |

1. Remove the control valve body cover (29).
2. Inspect the inside of the control valve body cover (29) for excessive sediment.

Did you find excessive amounts of sediment?

--

Go to Step 17

Go to Step 15

13 | Inspect the control valve body assembly (39) for the following conditions:

• | Stuck 2-3, 3-4 shift solenoid valve assembly (S2) - light gray (308)

• | Stuck M2 shift valve (426)

Did you find any of the above conditions?

--

Go to Step 22

Go to Step 16

14 | Inspect the control valve body assembly (39) for the following conditions:

• | Stuck 3-4, 4-5 shift solenoid valve assembly (S4) - blue (303)

• | Stuck U1 shift valve (386)

Did you find any of the above conditions?

--

Go to Step 22

Go to Step 16

15 | Inspect the control valve body assembly (39) for the following conditions:

• | Stuck M1 shift valve (389)

• | Stuck U1 shift valve (386)

• | Stuck U2 shift valve (392)

• | Stuck neutral relay valve (356)

• | Stuck line pressure control solenoid valve assembly (SLT) (316)

Did you find any of the above conditions?

--

Go to Step 22

Go to Step 16

16 | Has the control valve body been serviced within the past 3 months or 4 828 km (3,000 mi)? | -- | Go to Step 17 | Go to Step 22
17 | Inspect the following items:

• | Low clutch sprag (F2) (522)

• | Forward clutch (C1) (552)

• | 1-2, reverse clutch (B5) (620)

Is the action complete?

--

Go to Step 23

--

18 | Replace the input shaft speed sensor (73). Refer to Input Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 25 | --
19 | Replace the output shaft speed sensor (62). Refer to Output Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 25 | --
20 | Replace the reverse, 1st shift solenoid valve assembly (S1) - black (310). Is the replacement complete? | -- | Go to Step 25 | --
21 | Replace the 1-2, 2-3, reverse shift solenoid valve assembly (S3) - dark gray (300). Is the replacement complete? | -- | Go to Step 25 | --
22 | Repair or replace the control valve body assembly (39). Refer to Control Valve Body Cover Replacement . Is the action complete? | -- | Go to Step 24 | --
23 | Repair or replace the transmission. Refer to Transmission Replacement . Is the action complete? | -- | Go to Step 24 | --
24 |

1. Replace the transmission fluid. Refer to Transmission Fluid Replacement .
2. Inspect for the correct level of transmission fluid.
3. Add new fluid as necessary.

Important: The Reset Trans Adapts 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:

• | Reset oil life monitor to 100 percent.

• | Reset Trans Adapts.

Did you complete the above procedures?

--

Go to Step 25

--

25 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Operate the vehicle.
4. Select Specific DTC.
5. Enter DTC P0731.

Does the DTC reset?

--

Go to Step 2

Go to Step 26

26 | 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 | System OK