DTC P0751 1-2 Shift Solenoid Valve Performance. Pontiac Firebird 1997

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1997 🢒 Firebird 🢒 DTC 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance

DTC P0751 1-2 Shift Solenoid Valve Performance 3.8L, VIN K

OBD II Symbol Description Notice
Automatic Transmission Components VIN K

Circuit Description

The 1-2 Shift Solenoid Valve (1-2 SS Valve) controls fluid flow acting on the 1-2 shift valve and the 3-4 shift valve. The 1-2 SS Valve is a normally-open exhaust valve. Used with the 2-3 Shift Solenoid Valve (2-3 SS Valve), the 1-2 SS Valve allows four different shifting combinations.

If the PCM detects a 1-1-4-4 only or a 2-2-3-3 only shift pattern, then DTC P0751 sets. The pattern that the PCM detects depends on the mechanical failure. DTC P0751 is a type A DTC.

Conditions for Setting the DTC

•	No TP DTCs P0122 or P0123

•	No VSS DTCs P0502 or P0503

•	No TCC Stuck ON DTC P0742

•	No 1-2 SS Valve DTC P0753

•	No 3-2 SS Valve Assy. DTC P0785.

•	No TCC Sol. Valve DTC P0740.

•	No TCC PWM Sol. Valve Assy. DTC P1860.

•	No 2-3 SS Valve DTC P0758

•	No TFP Val Position Sw. DTC P1810

•	Previous shift time is greater than 0.0 seconds.

•	The gear range is D4.

•	The engine speed is greater than 400 RPM for 5 seconds and not in fuel cutoff.

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

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

•	All the above conditions have been met and the combination of Cases 1,2,3, and 4 or Cases 1,2,3, and 5 occur three consecutive times.

Case 1

-	Commanded 1-2 shift

-	The TP angle is 10-45%.

-	The TP angle is constant within +/-6%.

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

-	Within 2 seconds, the engine speed in 2nd gear must be 100 RPM greater than the last speed in 1st gear.

Case 2

-	Commanded 2-3 shift

-	The TP angle is 3-45%.

-	The TP angle is constant within +/-10%.

-	Vehicle speed is 16-105 km/h (10-65 mph).

-	Within 2 seconds, the engine speed in 3rd gear must be 100 RPM less than the last speed in 2nd gear.

Case 3

-	Commanded 3-4 shift

-	The TP angle is 2-45%.

-	The TP angle is constant within +/-7%.

-	The vehicle speed is 48-105 km/h (30-65 mph).

-	Within 0.7 seconds, the engine speed in 4th gear must be 1 RPM greater than the last speed in 3rd gear.

Case 4

-	Commanded 4th gear

-	The TCC is ON.

-	The TP angle is 7-35%.

-	The speed ratio is 0.95-1.2 (the speed ratio is the engine speed ÷ the output speed).

-	The TCC slip speed is 200-1000 RPM for greater than 4 seconds.

Case 5

-	Commanded 4th gear

-	The TCC is ON.

-	The TP is 7-35%.

-	The Speed ratio is 0.65-0.8 (the speed ratio is the engine speed ÷ the output speed).

-	The TCC slip speed is -20 to 40 RPM for greater than 4 seconds.

Action Taken When the DTC Sets

•	Use D2 pressure schedule

•	The PCM inhibits 3-2 downshifts if the vehicle speed exceeds 48 km/h (30 mph).

•	The PCM illuminates the Malfunction Indicator Lamp (MIL).

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

•	Verify that the transmission meets the specifications in the Shift Speed

•	Refer to Shift Solenoid Valve State and Gear Ratio .

•	More than one shift may occur because of other internal transmission failures.

Test Description

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

This step verifies that the TFP Valve Position Switch is functioning normally.

This step verifies that the following sequence occurs:

•	The scan tool commands all shifts.

•	All the shift solenoids respond properly.

•	Not all the shifts occur.

DTC P0751 1-2 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 , Section 6.

Install the Scan Tool ®.
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.
While the engine is operating, apply the brake pedal.

Select each transmission range Low, Dr 2, Dr 3, Overdrive, Park, and Reverse.

Does each selected transmission range match the TR Switch displayed on the scan tool?

Go to Step 3

Go to Pressure Switch Assembly Resistance Check

While the engine is operating, raise the drive wheels.
Put the transmission in D4 range. Using the scan tool, command 1st, 2nd, 3rd, and 4th gears while accelerating the vehicle.

Did you detect a 1-1-4-4 or 2-2-3-3 only shift pattern? (Road testing the vehicle may be necessary.)

Go to Step 4

Go to Diagnostic Aids

•	Examine the shift solenoid valves for an internal malfunction.

•	Inspect the shift solenoid valves for damaged seals.

•	Refer to the diagnosis tables.

Did you find and correct a problem?

Go to Step 5

After the repair is complete, select DTC.
Select Clear Info.
Operate the vehicle under the following conditions (only if the traffic and road conditions permit):

•	Hold the throttle at 20% and accelerate to . If the throttle moves more than 3%, stop the vehicle and start over.

•	Drive at 88 km/h (55 mph) for three km (two miles).

Select Specific DTC and enter DTC P0751.

Has the test run and passed?

System OK

Begin the diagnosis again. Go to Step 1

DTC P0751 1-2 Shift Solenoid Valve Performance 5.7L, VIN P

Automatic Transmission Components VIN P
OBD II Symbol Description Notice