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.

P0730

P0780

P0730

P0780

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

DTC P0730 and P0780 are Type A DTCs.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Information

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

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.

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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.