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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 Eldorado 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 DTC P0734

Circuit Description

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

If the PCM 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 VSS DTCs P0502 or P0503.
    • No AT ISS DTCs P0716 or P0717.
    • No IMS DTCs P1820, P1822, P1823, or P1825.
    • The engine run time is greater than 5 seconds.
    • The transmission is not in PARK or NEUTRAL.
    • The time since the gear select lever change is greater than 6 seconds.
    • The transmission fluid temperature is 20-133°C (68-271°F).
    • The TP angle is 10 percent or greater.
    • The vehicle speed is 5 km/h (3 mph) or greater.
    • The engine torque is 40-135 N·m (30-100 lb ft).

Conditions for Setting the DTC

The PCM commands 4th gear and one of the following conditions occurs for 4 seconds:

    • The gear ratio is greater than 3.11:1
    • 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 1.05:1 to 1.54:1
    • The gear ratio is 0.71:1 to 0.95:1
    • The gear ratio is less than 0.65:1

Action Taken When the DTC Sets
    • The PCM does not illuminate the malfunction indicator lamp (MIL).
    • SERVICE TRANSMISSION displays on the driver information center (DIC).
    • The PCM commands maximum line pressure.
    • The PCM freezes transmission adapt 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 P0734 in PCM history.

Conditions for Clearing the DIC/DTC
    • The PCM clears the DIC message when the condition no longer exists.
    • The PCM commands 4th gear and detects a correct 4th gear ratio for 1 second.
    • 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 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.

  2. This step verifies that the correct 4th gear ratio occurs for commanded 4th gear.

    3.

  3. This step tests for low line pressure.

DTC P0734

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls

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 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 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?

0.65:1-0.71:1

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 the following items:
    2. • The forward clutch assembly for:
       - Snap ring (818) out of position or damaged
       - Clutch plates (816, 817, 819, 840 and 841) slipping, dragging or damaged
       - Refer to Clutch Plate Diagnosis .
       - Apply ring (811) seized or damaged
       - Piston (807) cracked or damaged
       - Piston seals (808 and 809) rolled, worn or damaged
       - Release spring assembly (820) damaged
       - Housing checkball (437) blocked by debris or damaged
    • The 2nd clutch assembly for:
       - Piston assembly (430) cracked, worn seal or damaged
       - Clutch plates (431 through 435) slipping, dragging or damaged
       - Refer to Clutch Plate Diagnosis .
       - Return spring and retainer assembly (428) damaged
       - Air bleed checkball (437) blocked by debris or damaged
    • The 3rd clutch assembly for:
       - Snap ring (515) out of position or damaged
       - Clutch plates (610 through 613) slipping, dragging or damaged
       - Refer to Clutch Plate Diagnosis .
       - Return spring and retainer assembly (607) damaged
       - Piston assembly (606) cracked, worn seal or damaged
       - Piston checkballs (437) blocked by debris or damaged
    • The 4th servo assembly for:
       - Servo cover (524) cracked or damaged
       - Servo cover seal (525) rolled, worn or damaged
       - Piston (529) cracked or damaged
       - Piston seal (532) rolled, worn or damaged
       - Spring and retainer assembly (533) damaged
       - Servo pin (527) seized or damaged
    • The 4th band (523) for slipping, dragging or damage
    • The 4th band anchor pin (10) out of position or damaged
  2. Repair any of the above items as necessary.

    3. Refer to Transmission Overhaul in the 4T80-E section of the Transmission Unit Repair Manual.

Did you complete the repair?

--

Go to Step 7

--

7
  1. Change the AT fluid and filter.

    2. Refer to Fluid Filter Replacement.

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

    4. Important: The Clear TAPS 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 following:
    5. • 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:
    4. • The TFT is 20-133°C (68-271°F).
    • The engine torque is 40-135 N·m (30-100 lb ft).
    • Drive the vehicle in D4 with the TP angle greater than 10% in order to obtain a correct 4th gear ratio for 1 second.
  4. Select Specific DTC.
  5. Enter DTC P0734.

Has the test run and passed?

--

System OK

Go to Step 1