DTC P0751 1-2 Shift Solenoid Valve Performance. Buick Century 1996

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1996 🢒 Century 🢒 DTC 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance

Table 1:	Shift Solenoid State and Gear Ratio
Table 2:	DTC P0751 1-2 Shift Solenoid Performance

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

Circuit Description

The Powertrain Control Module (PCM) monitors the commanded gear and the speed ratio in order to identify a 1-2 Shift Solenoid Valve (1-2 SS Valve) problem.

When the PCM detects a 2-3 only or a 1-4 only shift pattern, then DTC P0751 sets. DTC P0751 is a type BDTC.

Conditions for Setting the DTC

•	No TP DTCs P0122 or P0123

•	No VSS DTC P0502

•	No TCC stuck ON DTC P0742

•	No 1-2 solenoid electrical DTC P0753

•	No 2-3 solenoid electrical DTC P0758

•	No TCC PWM solenoid electrical DTC P1860

•	No TCC enable solenoid electrical DTC P1864

•	The engine speed is greater than 500 RPM for 5 seconds.

•	Not in fuel shut off

•	The vehicle speed is greater than 8 km/h (5 mph).

•	The transmission temperature is 20-130°C (68-266°F).

•	The transmission range switch indicates D4.

•	The traction control is not active.

•	All of the above must occur twice and either fail-cases 1,2,3 and 4 or 1,2,3 and 5 are true twice.

Failure Criteria

Case 1:

•	1-2 shift commanded

•	The throttle position is 18-45% and is constant within 5%.

•	The vehicle speed is 8-72 km/h (5-45 mph).

•	When 2nd gear is commanded and within 2.5 seconds, engine speed is 110 RPM greater than the engine speed of the commanded 1st gear.

Case 2:

•	2-3 shift commanded

•	The throttle position is 18-45% and is constant within 5%.

•	The vehicle speed is 40-88 km/h (25-55 mph).

•	When 3rd gear is commanded and within 2.5 seconds, the engine speed is 150 RPM less than the engine speed of the commanded 2nd gear.

Case 3:

•	3-4 shift commanded

•	The throttle position is 18-45% and is constant within 3%.

•	The vehicle speed is 56-128 km/h (35-80 mph).

•	When 4th gear is commanded and within 2.5 seconds, the engine speed is 5 RPM greater than the engine speed of the commanded 3rd gear.

Case 4:

•	Fourth gear is commanded and the TCC is ON.

•	The throttle position is 7-37%.

•	The speed ratio is 39.3-42.3.

•	The TCC slip is 500-1000 RPM for more than 4 seconds.

Case 5:

•	Fourth gear is commanded and the TCC is ON.

•	The throttle position is 7-37%.

•	The speed ratio is 27.2-30.0.

•	The TCC slip is -20 to +25 RPM for more than 4 seconds.

Action Taken When the DTC Sets

•	The PCM inhibits downshifts to 2nd gear if the vehicle speed is greater than 48 km/h (30 mph).

•	The PCM illuminates the Malfunction Indicator Lamp (MIL) after two consecutive trips with a failure reported.

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

•	Check for PRNDL DTC P0705. A PRNDL DTC affects transmission operation. A PRNDL DTC may set DTC P0751 falsely.

•	Inspect the transmission fluid for sediment.

•	Inspect the transmission filter for debris.

Shift Solenoid State and Gear Ratio

Gear	1-2 Shift Solenoid	2-3 Shift Solenoid	Gear Ratio
1st	ON	ON	2.921:1
2nd	OFF	ON	1.568:1
3rd	OFF	OFF	1.000:1
4th	ON	OFF	0.705:1
Reverse	ON	ON	2.385:1

Test Description

The number below refers to the step numbers on the diagnostic chart.

Once the DTC is verified, replace the 1-2 shift solenoid.

DTC P0751 1-2 Shift Solenoid 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

Did you perform the fluid checking procedure?

Go to Step 3

Go to Transmission Fluid Check

Install the scan tool (tech 1) ®.
With the engine OFF, 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 for reference. The Clear Info function will erase the data.

Record the DTC Freeze Frame and Failure Records.
After verifying the DTC, replace the 1-2 SS Valve.

Refer to 1-2 Shift Solenoid Valve Replacement, On-Vehicle Service.

Is the replacement complete?

Go to Step 4

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

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

•	The traction control is not active.

•	The transmission fluid temperature is 20-130°C (68-266°F)

•	The engine speed is more than 500 RPM for 5 seconds.

•	The vehicle is not in fuel shut off.

•	The gear range is D4.

•	The vehicle speed is more than 8 km/h (5 mph).

•	All the conditions in the following cases must be met:

•

Case 1

-	The PCM commands a 1-2 shift.

-	The throttle position is 18-45% and constant by 5%.

-	The vehicle speed is 8-72 km/h (5-45 mph).

-	Within 2 seconds, the engine speed in 2nd gear must be 150 RPM less than the last engine speed in 1st gear.

•

Case 2

-	The PCM commands a 2-3 shift.

-	The throttle position is 18-45% and constant by 5%.

-	The vehicle speed is 40-88 km/h (25-55 mph).

-	Within 2.5 seconds, the engine speed in 3rd gear must be 150 RPM less than the last engine speed in 2nd gear.

•

Case 3

-	The PCM commands a 3-4 shift.

-	The throttle position is 18-45% and constant by 3%.

-	The vehicle speed is 56-128 km/h (35-80 mph).

-	Within 2 seconds, the engine speed in 4th gear must be 135 RPM less than the last engine speed in 3rd gear.

•

Case 4

-	The PCM commands 4th gear.

-	The throttle position is 7-37%.

-	The speed ratio is 27.2-30.0.

-	The PCM commands the TCC ON.

-	The TCC slip speed is -20 to +25 RPM for more than 5 seconds.

Select Specific DTC. Enter DTC P0751.

Has the test run and passed?

System OK

Begin the diagnosis again. Go to System Diagnosis Charts:

First and Fourth Gear Only - 1-2 Solenoid Stuck On Extended 1st Gear By Passing 2nd and 3rd then Shift to 4th

Second and Third Gear Only (1-2 Solenoid Stuck Off)