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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Monte Carlo 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T60-E 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance

Object Number: 28126 Size: SF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The 1-2 shift solenoid valve controls the fluid acting on the 1-2 and 3-4 shift valves. The PCM commands the solenoid ON or OFF by controlling the ground on the circuit. When the solenoid is OFF, the line pressure exhausts through the solenoid valve, allowing the 1-2 shift valve to be held by spring pressure in the second and third gear position. When the solenoid is ON, the exhaust flow is blocked, allowing line pressure to the 1-2 shift valve. This moves the 1-2 shift valve to the first and fourth gear position.

When the PCM detects a 1-1-4-4 or a 2-2-3-3 shift pattern under the test conditions, without an electrical malfunction, then DTC P0751 sets. DTC P0751 is a type A DTC.

Conditions for Running the DTC
    • No TP DTCs P0122 or P0123.
    • No VSS DTCs P0502 or P0503.
    • No TCC enable solenoid electrical DTC P0740.
    • 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.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • Not in fuel shut off.
    • The transmission range selector position is D4.
    • The vehicle speed is greater than 8 km/h (5 mph).
    • The transmission temperature is 20-130°C (68-266°F).
    • The traction control is not active.

Conditions for Setting the DTC

DTC P0757 will set if either fail cases 1, 2, 3 and 4 or 1, 2, 3 and 5 are true 3 times.

Failure Criteria

Case 1

    • 1-2 shift is commanded.
    • The throttle position is 18-55% and is constant within 3%.
    • The vehicle speed is 8-64 km/h (5-40 mph).
    • 2nd gear is commanded and, within 2.0 seconds, the engine speed is 100 RPM greater than the engine speed of the commanded 1st gear.

Case 2

    • 2-3 shift is commanded.
    • The throttle position is 10-55% and is constant within 10%.
    • The vehicle speed is 32-89 km/h (20-55 mph).
    • 3rd gear is commanded and, within 2.5 seconds, the engine speed is 130 RPM less than the engine speed of the commanded 2nd gear.

Case 3

    • 3-4 shift is commanded.
    • The throttle position is 5-40% and is constant within 7%.
    • The vehicle speed is 56-121 km/h (35-75 mph).
    • 4th gear is commanded and, within 1.0 second, the engine speed is 1 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 2-30%.
    • The speed ratio is 0.97-1.18.
    • The TCC slip is 500-1,000 RPM for more than 3 seconds.

Case 5

    • Fourth gear is commanded and the TCC is ON.
    • The throttle position is 2-30%.
    • The speed ratio is 0.68-0.82.
    • The TCC slip is 0 to +50 RPM for more than 3.0 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL).
    • The PCM inhibits commanded 3-2 downshifts if the vehicle speed is greater than 48 km/h (30 mph).

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 the PCM history if the vehicle completes 40 consecutive 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 is OFF long enough in order to power down the PCM.

Diagnostic Aids
    • Perform the transmission fluid checking procedure as requested in the table. Inspect the transmission fluid for color, sediment and debris.
    • Ensure that the scan tool commanded gear has correct solenoid states and ratio. Refer to Shift Solenoid Valve State and Gear Ratio table.

Test Description

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

  1. The Transmission Fluid Checking Procedure will examine the fluid for color, sediment and debris.

    2.

  2. Verify the DTC, and inspect shift solenoid and shift valve for sediment, debris or damage.

    3.

  3. If the problem is not corrected in step 3, replace the 1-2 shift solenoid.

DTC P0751 1-2 Shift Solenoid Performance

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Perform the transmission fluid checking procedure. Refer to Transmission Fluid Check .

Did you perform the transmission fluid checking procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3

  1. Install the Scan Tool .
  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. Using the Clear Info function erases the Freeze Frame and Failure Records.

  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Drive the vehicle in D4 range, under the following:

    6. Accelerate the vehicle, ensuring that the PCM commands 1st, 2nd, 3rd and 4th gear

Did you detect a 1-1-4-4 or 2-2-3-3 shift pattern?

--

Go to Step 4

Go to Diagnostic Aids

4

Inspect for the following conditions:

    • Shift solenoid screens 374 in the control valve body spacer plate assembly for sediment or debris.
    • 1-2 shift solenoid valve for a damaged or missing O-ring or cracked housing. Refer to Shift Solenoid Leak Test .
    • 1-2 shift valve sticking due to sediment, debris or damage.

Refer to Unit Repair.

Was a condition found and corrected?

--

Go to Step 6

Go to Step 5

5

Replace the 1-2 shift solenoid.

Refer to 1-2 Shift Solenoid Valve Replacement .

Is the replacement complete?

--

Go to Step 6

--

6

Perform the following in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • 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 pass cases must be met:

    Case 1

       - The PCM commands a 1-2 shift.
       - The throttle position is 18-55% and constant within + or - 3%.
       - The vehicle speed is 8-64 km/h (5-40 mph).
       - Within 2 seconds, the engine speed in 2nd gear must be 130 RPM less than the last engine speed in 1st gear.

    Case 2

       - The PCM commands a 2-3 shift.
       - The throttle position is 10-55% and constant within + or - 10%.
       - The vehicle speed is 32-89 km/h (20-55 mph).
       - Within 2.5 seconds, the engine speed in 3rd gear must be 130 RPM less than the last engine speed in 2nd gear.

    Case 3

       - The PCM commands a 3-4 shift.
       - The throttle position is 5-40% and constant within + or - 7%.
       - The vehicle speed is 56-121 km/h (35-75 mph).
       - Within 1.0 second, the engine speed in 4th gear must be 250 RPM less than the last engine speed in 3rd gear.

    Case 4

       - The PCM commands 4th gear.
       - The TCC is commanded ON.
       - The throttle position is 2-30%.
       - The speed ratio is 0.68-0.82.
       - The TCC slip speed is 0-50 RPM for more than 3 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0751.

Has the test run and passed?

--

System OK

Go to Step 1