DTC P0751 1-2 Shift Solenoid Valve Performance. Chevrolet Cavalier 1995

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1995 🢒 Cavalier 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T40-E 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance

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

Circuit Description

The 1-2 Shift Solenoid Valve (1-2 SS Valve) is a normally-open exhaust valve that, in conjunction with the 2-3 Shift Solenoid Valve (2-3 SS Valve), allows 4 different shifting combinations. The 1-2 SS Valve is attached to the control valve body, within the transmission.

The Powertrain Control Module (PCM) monitors the actual gear ratio, and compares the actual gear ratio with the commanded gear ratio. DTC P0751 sets under four conditions:

•	A stuck ON 1-2 SS Valve

•	A stuck OFF 1-2 SS Valve

•	A stuck ON 1-2 shift valve

•	A stuck OFF 1-2 shift valve

When the PCM detects an actual gear ratio that does not agree with the commanded gear, then DTC P0751 sets. DTC P0751 is a type A DTC.

Conditions for Setting the DTC

•	No Input Speed Sensor DTCs P0716 or P0717

•	No TFP Val. Position Sw. DTC P1810

•	No TP Sensor DTCs P0121, P0122, or P0123

•	No VSS DTC P0502

•	No shift solenoid DTCs P0753 or P0758

•	The engine is running.

•	The TFP Val. Position Sw. is not indicating Park, Reverse, or Neutral.

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

•	The TP is greater than 15%.

•	The engine speed is less than 6500 RPM.

•	The MAP is 40-105 kPa.

•	The transmission fluid temperature is greater than 20°C (68°F).

All of the above conditions are true, and any one of the following failure cases occurs twice:

Case 1:

•	The PCM commands 1st gear and the gear ratio is 1:1.54-1:1.71 (2nd gear) for 2 seconds.

•	The PCM commands 4th gear and the gear ratio is 1:0.93-1:1.05 (3rd gear) for 6 seconds.

Case 2:

•	The PCM commands 2nd gear and the gear ratio 1:2.87-1:3.13 (1st gear) for 4 seconds.

•	The PCM commands 3rd gear and the gear ratio is 1:0.67-1:0.72 (4th gear) for 5 seconds.

Action Taken When the DTC Sets

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

•	The PCM freezes shift adapts from being updated.

•	The PCM inhibits TCC engagement.

•	The PCM commands maximum line pressure.

•	The PCM commands a soft landing to 2nd gear.

•	DTC P0751 is stored in the PCM history.

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

•	If you clear DTC P0751, and then cannot reset DTC P0751, inspect for the following conditions:

-	Fluid contamination

-	Plugged oil circuits

-	Restricted oil circuits

•	Inspect for a stuck throttle position (TP) sensor.

Test Description

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

This Step verifies that the gear ratio is correct for the commanded gear.

This Step tests for a mechanical or hydraulic problem causing the 1-2 SS valve to be stuck ON, or the circuit to be applied.

This Step tests for a mechanical or hydraulic problem causing the 1-2 SS valve to be stuck OFF, or the circuit to be released.

P0751

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 in Engine Controls - 2.3L

Have you performed the transmission 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.
Use the scan tool snapshot mode in order to record current gear and gear ratio.
Drive the vehicle in D4, in order to obtain 1-2, 2-3 and 3-4 shifts with a TP greater than 20% and a vehicle speed greater than 11 km/h (7 mph) for 6 seconds.

Is the current gear 2nd, and the gear ratio within the specified range?

1:2.87-1:3.13

Go to Step 5

Go to Step 4

Is the current gear 1st, and the gear ratio within the specified range?

1:1.54-1:1.71

Go to Step 6

Go to Step 5

Is the current gear 3rd, and the gear ratio within the specified range?

1:0.67-1:0.72

Go to Step 7

Go to Step 6

Is the current gear 4th, and the gear ratio within the specified range?

1:0.93-1:1.05

Go to Step 8

Go to Diagnostic Aids

Inspect the 1-2 shift circuit for the following conditions:

•	1-2 Shift Solenoid Valve (1-2 SS Valve) mechanically stuck ON.

•	1-2 shift valve stuck in the applied position.

Repair the circuit.

Refer to Unit Repair.

Did you find and correct the condition?

Go to Step 9

Inspect the 1-2 shift circuit for the following conditions:

•	1-2 Shift Solenoid Valve (1-2 SS Valve) mechanically stuck OFF.

•	Damaged 1-2 SS Valve O-ring

•	1-2 shift valve stuck in the released position.

Repair the circuit.

Refer to Unit Repair.

Did you find and correct the condition?

Go to Step 9

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

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

•	Drive the vehicle in D4.

•	Allow the transmission to shift through all the gears.

•	Monitor the current gear and gear ratios. The actual gear ratios must match the commanded gears for 3 seconds, for all gears.

Select Specific DTC. Enter DTC P0751.

Has the test run and passed?

System OK

Begin the diagnosis again. Go to Step 1