GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1996 🢒 Aurora 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 DTC P0756 2-3 (B) Shift Solenoid Performance
Table 1: Shift Solenoid Valve State and Gear Ratio
Table 2: DTC P0756 2-3 Shift Solenoid Valve Performance

Object Number: 20677 Size: LF

Circuit Description

The Powertrain Control Module (PCM) identifies a 2-3 shift solenoid valve performance problem by monitoring the commanded gear versus the gear ratio.

When the PCM detects the gear ratio outside the limits for a particular commanded gear, then DTC P0756 sets. DTC P0756 is a Type A DTC.

Conditions for Setting the DTC
    • No MAF DTCs P0101, P0102 or P0103 are set.
    • No TP DTCs P0121, P0122 or P0123 are set.
    • No VSS DTCs P0502 or P0503 are set.
    • No A/T ISS DTCs P0716 or P0717 are set.
    • No 1-2 shift solenoid valve electrical DTC P0753 is set.
    • No 2-3 shift solenoid valve electrical DTC P0758 is set.
    • No TFP Val. Position Sw. DTC P1810 is set.
    • The engine has been running for more than 5 seconds.
    • The vehicle speed is more than 6 km/h (4 mph).
    • The throttle angle is greater than 11°.
    • A shift is not in progress.
    • Not in fuel shut off.
    • The Automatic Transmission Fluid Temperature is greater than 30°C (86°F).
    • The TFP Val. Position Sw. indicates D1, D2, D3 or D4.

Failure Case #1

    • First gear is commanded.
    • The gear ratio is 0.65-0.71 for 1 second.
    • Delivered torque is greater than 82 N·m (60 lb ft).

Failure Case #2

    • Second gear is commanded.
    • The gear ratio is 0.95-1.05 for 0.5 seconds.
    • Delivered torque is greater than 82 N·m (60 lb ft).

Failure Case #3

    • Third gear is commanded.
    • The gear ratio is 1.54-1.71 for 4 seconds.
    • Delivered torque is greater than 82 N·m (60 lb ft).

Failure Case #4

    • Fourth gear is commanded.
    • The gear ratio is 2.87-3.11 for 1 second.
    • Delivered torque is greater than 22 N·m (16 lb ft).

Action Taken When the DTC Sets
    • The PCM illuminates the Malfunction Indicator Lamp (MIL).
    • SERVICE ENGINE SOON displays on the Driver Information Center (DIC).
    • The PCM commands 2nd gear.
    • The PCM commands default line pressure.
    • The PCM inhibits Torque Converter Clutch.
    • The PCM disables steady state adapts.
    • The PCM disables garage shift adapts.
    • The PCM inhibits torque management.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
    • A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
    • The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Inspect the transmission fluid for sediment.
    • Inspect the transmission filter for debris.
    • The customer may experience an engine flair or neutral in 4th gear.

Shift Solenoid Valve State and Gear Ratio

Gear Range

1-2 Shift Soleniod

2-3 Shift Solenoid

Ratio

First

ON

OFF

2.87-3.11

Second

OFF

OFF

1.54-1.71

Third

OFF

ON

0.95-1.05

Fourth

ON

ON

0.65-0.71

Reverse

ON

OFF

2.02-2.23

Test Description

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

Important: Do not drive the vehicle for an extended period of time, as additional internal damage may occur.

  1. This Step verifies that the Powertrain On-Board Diagnostic System Check was performed.

    2.

  2. This Step verifies that the transmission fluid checking procedure was performed.

    3.

  3. This Step verifies that DTC P0756 is set. Set up data pairs on the scan tool. Drive the vehicle while commanding First gear with the scan tool.

    4.

  4. This Step verifies that the gear ratio indicates a Fourth gear start, and the vehicle does not achieve First gear. The list of components should be inspected and repaired, if faulty.

    5.

  5. This Step drives the vehicle while commanding a 1-2 upshift with the scan tool.

    6.

  6. This Step verifies that the gear ratio indicates Third gear and the vehicle does not achieve Second gear. The list of components should be inspected and repaired, if faulty.

    7.

  7. This Step drives the vehicle while commanding a 2-3 upshift with the scan tool.

    8.

  8. This Step verifies that the gear ratio indicates Second gear and the vehicle does not achieve Third gear. The list components should be inspected and repaired, if faulty.

    9.

  9. This Step drives the vehicle while commanding a 2-3 upshift with the scan tool.

    10.

  10. This Step verifies that the gear ratio indicates First gear and the vehicle does not achieve Fourth gear. The list of components should be inspected and repaired, if faulty.

DTC P0756 2-3 Shift Solenoid Valve Performance

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2

Have you performed the fluid checking procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3
  1. Install the scan tool (tech 1) .
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Select A/T Outputs, Shift Trans.
  5. Monitor the following data pairs:
    6. • Current gear
    • Gear ratio
  6. Accelerate the vehicle and command First gear.

Is the gear ratio within the specified parameters?

0.65-0.71

Go to Step 4

Go to Step 5

4

Inspect and repair the following items:

    • A damaged Lo/Rev servo apply pin
    • A stuck 2-3 shift valve
    • Damaged or leaking oil seals (support seals)
    • The support stud from the case to the forward clutch is damaged or broken
    • The Lo roller clutch assembly is worn or damaged
    • The forward clutch piston is damaged or cracked
    • The forward clutch piston seals are rolled, cut or damaged
    • The forward sprag is damaged or not holding
    • Check ball #8 is missing

Refer to Unit Repair.

Is the inspection and repair complete?

--

Go to Step 11

--

5

Accelerate the vehicle and command a 1-2 upshift.

Is the gear ratio within the specified parameters?

0.95-1.05

Go to Step 6

Go to Step 7

6

Inspect and repair the following items:

    • The 2nd clutch plates are burned or damaged
    • The 2nd clutch pistons assembly is cracked or damaged
    • The 2nd clutch return spring and retainer assembly is broken or out of position
    • The 2nd clutch piston seals are rolled, damaged or leaking
    • The 2-3 shift valve is stuck

Refer to Unit Repair.

Is the inspection and repair complete?

--

Go to Step 11

--

7

Accelerate the vehicle and command a 2-3 upshift.

Is the gear ratio within the specified parameters?

1.54-1.71

Go to Step 8

Go to Step 9

8

Inspect and repair the following items:

    • The 3-4 shift valve bore plug is misassembled
    • The exhaust valve cup plug or the exhaust valve are improperly installed on the driven sprocket support
    • The 3rd clutch plates are burned or the splines are damaged
    • The 3rd clutch piston is cracked or damaged, or the checkball is damaged
    • The 3rd clutch seals on piston are cut or rolled
    • The checkballs (437) are missing or stuck
    • Debris in the 2-3 Shift Solenoid Valve

Refer to Unit Repair.

Is the inspection and repair complete?

--

Go to Step 11

--

9

Accelerate the vehicle and command a 3-4 upshift.

Is the gear ratio within the specified parameters?

2.87-3.11

Go to Step 10

Go to Diagnostic Aids

10

Inspect and repair the following items:

    • Debris in the 2-3 Shift Solenoid Valve
    • The 4th band is burned, slipping or missing
    • The 4th servo pin is broken or seized
    • The 4th servo cover seal is rolled, cut or damaged
    • The 4th servo piston seal is rolled, cut or damaged
    • The 4th servo cover is cracked
    • The 3-4 shift valve bore plug is misassembled

Refer to unit repair

Is the inspection and repair complete?

--

Go to Step 11

--

11

In order to verify your repair, perform the following procedure:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. 3.1. Road test the vehicle with the gear select lever in D4.
    3.2. Ensure that all four gears are achieved.
  4. Select Specific DTC. Enter DTC P0756.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1