For 1990-2009 cars

## DTC P0734 3.0L (L81)

### Circuit Description

The TCM calculates gear ratio based on data from the automatic transmission input shaft speed and vehicle speed sensors. The TCM compares the known transmission gear ratio to a calculated ratio for each commanded gear.

If the TCM detects an incorrect 4th gear ratio, indicating excessive slip or drag within the transmission, then DTC P0734 sets. DTC P0734 is a type C DTC.

### Conditions for Running the DTC

• | No TP DTCs P0121, P0122 or P0123.

• | No MAP DTCs P0107 or P0108.

• | No MAF DTCs P0101, P0102, P0103.

• | No VSS DTCs P0502 or P0503.

• | No AT ISS DTCs P0716 or P0717.

• | No 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 is 50-130°C (122-266°F).

• | The TP angle is greater than 15 percent.

• | The vehicle speed is 8 km/h (5 mph) or greater.

### Conditions for Setting the DTC

The TCM commands 3rd gear and one of the following conditions occurs for 7 seconds:

• | The gear ratio is greater than 3.13:1

• | 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 0.61:1

### Action Taken When the DTC Sets

• | The TCM does not request the 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 P0733 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 input shaft speed sensor circuit conditions.

• | Inspect for intermittent vehicle speed sensor 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. This step verifies that the correct 4th gear ratio occurs for commanded 4th gear.

3. This step tests for low line pressure.

#### DTC P0734

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls- 3.0L (L81)
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 Checking Procedure
4 |

1. Install a scan tool.
2. 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 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 D4 and record the 4th gear ratio.

Is the 4th gear ratio within the specified parameters?

0.61:1-0.71:1

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 Procedure
6 |

1. Inspect the following items:

• | The Intermediate/Fourth Band and Servo for:

- | Servo Piston (77) broken or binding.

- | Servo Piston Seals (78, 79) leaking.

- | Servo Pin (76) and Servo Spring (75) binding.

- | Servo Cover (80) broken, loose or leaking.

- | Band (100) broken, worn or out of position.

- | Refer to Intermediate Fourth Band Removal

- | or Intermediate/Fourth Servo Disassemble in Unit Repair.

• | The Direct Clutch Plates slipping, dragging or damaged.

• | Refer to Clutch Plate Diagnosis

• | The Direct Clutch assembly for:

- | Piston and Seal Assembly (518) binding, cracked or leaking.

- | Snap Ring (520) out of position.

- | Housing Retainer and ball Assembly missing or out of position.

- | Return Spring (519) binding.

- | Direct/Coast Clutch Input Shaft and Housing (502) damaged, cracked or restricted oil feed holes.

- | Refer to Direct/Coast Clutch, Reaction Carrier Disassemble in Unit Repair.

• | The Driven Sprocket Support Seals (403) leaking.

• | Refer to Driven Sprocket Support Assembly Disassemble in Unit Repair.

2. Repair any of the above items as necessary.

Did you complete the repair?

--

Go to Step 7

--

7 |

1. Change the AT fluid and filter.

Refer to Automatic Transmission Fluid Filter and Seal Replacement in Unit Repair.

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

Important: The Clear TAPS 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%.

• | Clear TAPS.

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:

• | The TFT is 50-130°C (122-266°F).

• | Drive the vehicle in D4 with the TP angle greater than 15% in order to obtain a correct 4th gear ratio for 7 seconds.

4. Select Specific DTC.
5. Enter DTC P0734.

Has the test run and passed?

--

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 in Engine Controls - 3.0L (L81) | System OK