DTC P0756 2-3 Shift Solenoid Valve Performance. Cadillac Eldorado 1999

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 DTC P0756 2-3 Shift Solenoid Valve Performance

Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The PCM identifies a 2-3 shift solenoid valve performance problem by monitoring the commanded gear ratio versus the actual gear ratio.

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

Conditions for Running the DTC

•	No MAF DTCs P0101, P0102 or P0103.

•	No TP DTCs P0121, P0122 or P0123.

•	No VSS DTCs P0502 or P0503.

•	No A/T ISS DTCs P0716 or P0717.

•	No 1-2 shift solenoid valve electrical DTC P0753.

•	No 2-3 shift solenoid valve electrical DTC P0758.

•	No TFP manual valve position switch DTC P1810.

•	No TCC PWM solenoid valve DTC P1860.

•	The engine run time is greater than 5 seconds.

•	The engine is not in fuel cut off.

•	The TFP manual valve position switch indicates D1, D2, D3 or D4.

•	The automatic transmission fluid temperature is greater than -18°C (0°F).

•	A shift is not in progress.

•	The throttle angle is greater than 11 degrees.

•	The vehicle speed is greater than 6 km/h (4 mph).

Conditions for Setting the DTC

DTC P0756 sets when Case 1 and Case 2 are true, or when Case 3 and Case 4 are true.

Case 1

•	First gear is commanded.

•	The gear ratio is 0.65:1-0.71:1 for 1 second.

•	Delivered torque is greater than 82 N·m (60 lb ft).

Case 2

•	Second gear is commanded.

•	The gear ratio is 0.95:1-1.05:1 for 0.5 seconds.

•	Delivered torque is greater than 82 N·m (60 lb ft).

Case 3

•	Third gear is commanded.

•	The gear ratio is 1.54:1-1.71:1 for 4 seconds.

•	Delivered torque is greater than 82 N·m (60 lb ft).

Case 4

•	Fourth gear is commanded.

•	The gear ratio is 2.87:1-3.11:1 for 1 second.

•	Delivered torque is greater than 15 N·m (12 lb ft).

Action Taken When the DTC Sets

•	The PCM illuminates the malfunction indicator lamp (MIL).

•	SERVICE ENGINE SOON, SERVICE TRANSMISSION displays on the driver information center (DIC).

•	The PCM commands 2nd gear.

•	The PCM commands default line pressure.

•	The PCM inhibits TCC engagement.

•	The PCM freezes steady state adapts.

•	The PCM freezes garage shift adapts.

•	The PCM stores DTC P0756 in PCM history.

Conditions for Clearing the MIL/DTC

•	The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.

•	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 an 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

•	Inspect the transmission fluid for sediment.

•	Inspect the transmission filter for debris.

•	The customer may experience an engine flair or neutral in 4th gear.

•	Refer to Shift Solenoid Valve State and Gear Ratio table.

Test Description

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

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

This step verifies that the Transmission Fluid Checking Procedure was performed.

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.

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.

DTC P0756 2-3 Shift Solenoid Valve Performance

Step

Action

Value(s)

Yes

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

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Was the Transmission Fluid Checking Procedure performed?

Go to Step 3

Go to Transmission Fluid Check

Install the Scan Tool .
Turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.

Record the Freeze Frame and Failure Records.
Clear the DTCs.
Using the scan tool, enter the Shift Transmission function.
Monitor the Current Gear and Gear Ratio data pairs.
Accelerate the vehicle and command FIRST gear.

Is the gear ratio within the specified parameters?

0.65:1-0.71:1

Go to Step 4

Go to Step 5

Inspect 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

Repair or replace any of the items as necessary.

Refer to Unit Repair.

Is the repair complete?

Go to Step 11

Accelerate the vehicle and command a 1-2 upshift.

Is the gear ratio within the specified parameters?

0.95:1-1.05:1

Go to Step 6

Go to Step 7

Inspect 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

Repair or replace any of the items as necessary.

Refer to Unit Repair.

Is the repair complete?

Go to Step 11

Accelerate the vehicle and command a 2-3 upshift.

Is the gear ratio within the specified parameters?

1.54:1-1.71:1

Go to Step 8

Go to Step 9

Inspect the following items:

•	The 3-4 shift valve bore plug is mis-assembled

•	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 ball check valves (437) are missing or stuck

•	Debris in the 2-3 shift solenoid valve

Repair or replace any of the items as necessary.

Refer to Unit Repair.

Is the repair complete?

Go to Step 11

Accelerate the vehicle and command a 3-4 upshift.

Is the gear ratio within the specified parameters?

2.87:1-3.11:1

Go to Step 10

Go to Diagnostic Aids

Inspect for 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 mis-assembled

Repair or replace any of the items as necessary.

Refer to Unit Repair

Is the repair complete?

Go to Step 11

Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Operate the vehicle under the following conditions:

3.1.	Road test the vehicle with the gear select lever in D4.

3.2.	Ensure that all four gears are achieved.

Select Specific DTC. Enter DTC P0756.

Has the test run and passed?

System OK

Go to Step 1