GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Classic 🢒 DTC 🢒 DTC P0730

Circuit Description

The powertrain control module (PCM) calculates gear ratio based on the transmission input and output speeds. The PCM compares the known transmission gear ratio to the calculated ratio for the selected gear range.

When the PCM detects an unknown transmission gear ratio, then DTC P0730 sets. DTC P0730 is a type C DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0730 Incorrect Gear Ratio

Conditions for Running the DTC
    • No MAP sensor DTCs P0106, P0107, or P0108.
    • No TP sensor DTCs P0122 or P0123.
    • No VSS DTCs P0502 or P0503.
    • No ISS DTCs P0716 or P0717.
    • The engine is running for greater than 5 seconds.
    • The transmission fluid pressure (TFP) manual valve position switch is not indicating PARK or NEUTRAL.
    • The time since the gear select lever change is greater than 6 seconds.
    • The transmission fluid temperature (TFT) is greater than 20°C (68°F).
    • The throttle position (TP) is greater than 15 percent.
    • The vehicle speed is greater than 8 km/h (5 mph).
    • The engine torque is greater than 68 N·m (50 lb ft).

Conditions for Setting the DTC

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 PCM does not illuminate the malfunction indicator lamp (MIL).
    • The PCM commands maximum line pressure.
    • The PCM freezes transmission adaptive functions.
    • The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.
    • The PCM stores DTC P0730 in PCM history.

Conditions for Clearing the DTC
    • A scan tool can clear the DTC.
    • The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
    • The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Inspect for intermittent input speed sensor (ISS) circuit conditions.
    • Inspect for intermittent output speed sensor (OSS) circuit conditions.
    • Inspect for an incorrect calibration.
    •  Refer to Range Reference .
    • Ensure the wiring harness is not stretched too tightly or other components are pressing on the connector body. Also, inspect for proper clearance to any other components and wiring. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

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.

  2. This step verifies that the correct gear ratios occur for commanded gears.

    3.

  3. This step tests for low line pressure.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Visually inspect the transmission cooling system for fluid leaks.
  2. Repair any 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?

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Go to Step 4

Go to Transmission Fluid Check

4

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

    3. 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 PCM.

  3. Record the DTC Failure Records.
  4. Clear the DTC.
  5. Use the scan tool snapshot mode in order to record the transmission gear ratios.
  6. Drive the vehicle in transmission gear ranges 1, 2, 3, and D with the TP greater than 15%, and the vehicle speed greater than 8 km/h (5 mph).
  7. Record each transmission gear ratio.

Did the gear ratio match the specified ranges?

Reverse: 2.02:1-2.23:1

1st: 2.87:1-3.13:1

2nd: 1.54:1-1.71:1

3rd: 0.91:1-1.07:1

4th: 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

6
  1. Inspect for excessive clutch wear. Refer to Clutch Plate Diagnosis .
  2. Repair as necessary. Refer to Second Clutch Plates Removal , Forward Clutch Assembly Disassemble or Direct/Coast Clutch, Reaction Carrier Disassemble in Transmission Unit Repair Manual.

Did you complete the repair?

--

Go to Step 7

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7
  1. Change the AT fluid and filter. Refer to Automatic Transmission Fluid Filter and Seal Replacement .
  2. Inspect the transmission fluid for correct level.
  3. Add new fluid as necessary.

    4. Important: The Clear TAP function will clear all adapt cells. This may affect transmission performance. The PCM will update the adapt cell values as the vehicle is driven.

  4. Use the scan tool in order to perform the Clear TAP function.

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. Drive the vehicle with the throttle greater than 15% in order to obtain any one of the following gear ratios for 7 seconds.
    4. • Reverse: 2.02:1-2.23:1
    • 1st: 2.87:1-3.13:1
    • 2nd: 1.54:1-1.71:1
    • 3rd: 0.91:1-1.07:1
    • 4th: 0.61:1-0.71:1
  4. Select Specific DTC.
  5. Enter DTC P0730.

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 - Vehicle in Vehicle DTC Information

System OK