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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Restraints 🢒 SIR 🢒 DTC P0730

Circuit Description

The powertrain control module (PCM) calculates the gear ratio based on the automatic transmission input shaft speed sensor (AT ISS) and output shaft speed sensor (AT OSS) input. The PCM compares the known transmission gear ratio to the calculated ratio for the selected gear ranges. Refer to Shift Solenoid Valve State and Gear Ratio .

If 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 DTC P0106, P0107, or P0108.
    • No TP sensor DTC P0121, P0122, or P0123.
    • No AT OSS DTC P0502 or P0503.
    • No ISS DTC P0716 or P0717.
    • No TFP manual valve position switch DTC P1810.
    • No 4WD low DTC P2771.
    • The system voltage is 8-18 volts for more than 0.5 seconds.
    • The vehicle speed is greater than 8 km/h (5 mph).
    • The throttle angle is greater than 15 percent.
    • The TFT is greater than 20°C (68°F).
    • No gear range change for greater than 6 seconds.
    • The engine torque must be 108-576 N·m (80-425 lb ft).
    • The engine is running greater than 7 seconds.
    • The transfer ratio is 0.95-1.05.
    • The engine vacuum is 0-105 kPa (0-15 psi).

Conditions for Setting the DTC

One of the following conditions occur for 10 seconds:

    • The gear ratio is greater than 2.51:1.
    • The gear ratio is 2.12:1 to 2.43:1.
    • The gear ratio is 1.51:1 to 2.05:1.
    • The gear ratio is 1.03:1 to 1.44:1.
    • The gear ratio is less than 0.97:1.

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 shift adapts.
    • 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 clears the DTC from PCM history.
    • 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 fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • A false or incorrect AT OSS or AT ISS signal can set DTC P0730.
    • DTC P0894 detects an incorrect gear ratio in fourth gear with the torque converter clutch (TCC) applied.
    • Inspect for any improperly installed aftermarket equipment.
    • Sticking or contamination of shift valves may cause intermittent incorrect gear ratios.
    • Refer to Shift Solenoid Valve State and Gear Ratio .
    • DTC P0730 defaults to an elevated line pressure which may result in partial TCC apply. This may produce an idle surge that could stall the engine.

Test Description

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

  1. This step tests the indicated range signal to the actual selected range. A faulty TFP manual valve position switch could set DTC P1810.

    2.

  2. This step tests for proper ratios in each commanded gear state.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Perform the Transmission Fluid Checking Procedure. Refer to Transmission Fluid Check .

Did you perform the Transmission Fluid Checking Procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3

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

    3. Important: Before clearing the DTCs, 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 DTCs.
  5. Start the engine.
  6. Apply the parking brake, and select each transmission range: D1, D2, D3, D4, N, R, and P.

Refer to Transmission Fluid Pressure Manual Valve Position Switch Logic .

Does the scan tool TFP switch A/B/C display match each selected gear range?

--

Go to Step 4

Go to DTC P1810

4

  1. Drive the vehicle in D3 with the throttle position (TP) sensor above 15%.
  2. Operate the vehicle above 11 km/h (7 mph) for greater than 2 seconds in each specified gear range.
  3. Use the scan tool snapshot mode to record the transmission gear ratio for each commanded gear range: REVERSE, 1st, 2nd, and 3rd.

Are the commanded gear ratios within the values for each specified gear range?

Reverse: 2.05:1 to 2.12:1

1st: 2.43:1 to 2.51:1

2nd: 1.44:1 to 1.51:1

3rd: 0.97:1 to 1.03:1

Go to Diagnostic Aids

Go to Step 5

5
  1. Connect the J 21867 pressure gage to the transmission line pressure tap.
  2. Perform the Line Pressure Check Procedure. Refer to Line Pressure Check .

Is the line pressure within specifications for each selected gear range?

--

Go to Step 6

Go to Symptoms - Automatic Transmission

6
  1. Inspect for excessive clutch wear. Refer to Clutch Plate Diagnosis .
  2. Repair the condition as necessary. Refer to Direct Clutch Assembly Disassemble , Forward Clutch Assembly Disassemble , 4th Clutch Assembly Disassemble and Overrun Clutch Assembly Disassemble in Transmission Unit Repair Manual.

Did you complete the repair?

--

Go to Step 8

Go to Step 7

7
  1. Change the AT fluid and filter. Refer to Automatic Transmission Fluid and Filter Replacement .

    2. 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.

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

Did you complete the above procedure?

--

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:
    4. • Drive the vehicle in REVERSE, 1st, 2nd, and 3rd gear.
    • The PCM must see valid gear ratios for the commanded gear.
  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

System OK