For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0730: Incorrect Gear Ratio
DTC P0780: Incorrect Shift Pattern

### 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.

### Conditions for Running the DTC

#### P0730

• | No Transmission Range (TR) Switch DTC P0705.

• | No Speed Sensor DTCs P0717, P0722.

• | No transmission fluid temperature (TFT) Sensor DTCs P0711-P0713.

• | 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, or P0980.

• | Output speed is greater than 500 RPM.

• | Throttle position is greater than 10 percent.

• | Time since Transmission Range Switch change greater than 7 seconds.

• | Time since transmission shift greater than 3 seconds.

• | Not in 1st gear.

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

• | TR Switch equals D, 3, 2, or 1.

#### P0780

• | No TR Switch DTC P0705.

• | No Shift Solenoid (SS) Control Circuit DTCs P0973, P0974, P0976, P0977, P0979, or P0980.

• | Not in Emergency Mode.

• | Time since TR Switch change is greater than 3 seconds.

• | Not shifting.

• | Not neutral control.

• | TR Switch equals D, 3, or 2.

### Conditions for Setting the DTC

#### P0730

• | The TCM detects that the actual gear ratio and the expected gear ratio differ by more than 10 percent.

• | The condition exists for more than 5 seconds.

#### P0780

The TCM detects that a downshift resulted in an input speed greater than allowed for 1.28 second.

### Action Taken When the DTC Sets

• | DTC P0730 and P0780 are Type A DTCs.

• | The transmission will operate in 4th gear in D range, Reverse in R range.

### Conditions for Clearing the DTC

DTC P0730 and P0780 are Type A DTCs.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Transmission General Information

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Perform the Transmission Fluid Check to verify correct fluid level and condition. The transmission fluid level should be within the crosshatch band and the transmission fluid should be red or dark brown.

⇒ | If the transmission fluid is low or discolored, refer to Transmission Fluid Draining , Transmission Fluid Check.

2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### 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 shift solenoid valve or a stuck U1 shift valve. Refer to Control Valve Body Assembly Disassemble procedure.

2. Firmly apply the parking brake, select D, drive, using the Shift Control.
3. Observe the scan tool Torque Converter Slip parameter with the brake pedal released. The parameter should be greater than 90 percent.

⇒ | If the Torque Converter Slip parameter 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. Refer to Control Valve Body Assembly Disassemble.

• | 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 shift solenoid 3 valve assembly. Refer to Control Valve Body Assembly Disassemble.

• | Perform a line pressure test. Refer to Line Pressure Check procedure.

• | Remove the Control valve body cover. Refer to Control Valve Body Cover Removal procedure.

• | 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. Refer to Forward Clutch and Overdrive and Coast Clutch Removal , Forward Clutch and Overdrive and Coast Clutch Installation , Forward Clutch Assembly Assemble , and Reverse Clutch Housing and Input Shaft Assembleprocedures.

• | Inspect the control valve body assembly for the following conditions. The conditions should not be found.

- | Stuck shift pressure relay valve

- | Stuck M1 shift valve

- | Line pressure control solenoid valve assembly stuck closed

- | Refer to Control Valve Rear Body Disassemble and Control Valve Body Disassemble - Middle.

⇒ | If any of the above conditions are found, replace the valve body assembly. Refer to Control Valve Body Assembly Installation , Control Valve Body Assembly Removalprocedures.

• | 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. Refer to Control Valve Body Assembly Installation , Control Valve Body Assembly Removal procedures.

4. If all circuits and components test normal, replace the transmission.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Transmission Fluid Draining

• | Transmission Fluid Check

• | Control Valve Body Assembly Disassemble

• | Line Pressure Check

• | Control Valve Body Cover Removal

• | Forward Clutch and Overdrive and Coast Clutch Removal

• | Forward Clutch and Overdrive and Coast Clutch Installation

• | Forward Clutch Assembly Assemble

• | Reverse Clutch Housing and Input Shaft Assemble

• | Control Valve Rear Body Disassemble

• | Control Valve Body Disassemble - Middle

• | Control Valve Body Assembly Installation

• | Control Valve Body Assembly Removal