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Makes 🢒 Cadillac 🢒 2000 🢒 Catera 🢒 DTC 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance - No Second or Third Gear

Object Number: 398666 Size: LF
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The 1-2/3-4 shift solenoid (SS) valve is a normally closed shift solenoid that controls the positioning of the 1-2/3-4 shift valve. When de-energized (off), the solenoid is closed and blocks D32/1-2 fluid from acting on the solenoid end of the 1-2/3-4 shift valve. When energized (on), the solenoid opens and D32/1-2 fluid pressure flows through the solenoid, acts on the solenoid end of the shift valve and moves the valve against spring force.

When the TCM detects a 1-1/4-4 shift pattern, then DTC P0751 will set. DTC P0751 is a type B DTC.

Conditions for Running the DTC
    • Transmission is in drive (D4).
    • No Trans Range Switch DTC P0705.
    • No Output Speed Sensor DTC P0722.
    • No 1-2/3-4 SS Valve DTC P0753.
    • No 2-3 SS Valve DTC P0758.
    • No TCM Internal - Watchdog Operation DTC P1600.
    • No TCM System Reset DTC P1625.
    • No TCC Enable Solenoid Circuit - Electrical DTC P0743.
    • No Throttle Position Signal DTC P1890.

All the above conditions must be present, plus one of the following conditions:

Condition 1:

    • The commanded gear is 2nd for greater than 0.7 seconds.
    • Throttle position is greater than 30.8 percent.
    • Engine speed is 3,104-3,904 RPM.
    • Transmission output speed is greater than 992 RPM.
    • Engine torque is greater than 50 N·m (68 lb ft).

Condition 2:

    • The commanded gear is 3rd for greater than 0.7 seconds.
    • Throttle position is greater than 24.9 percent.
    • Engine speed is 1,216-2,016 RPM.
    • Transmission output speed is greater than 2,016 RPM.
    • Engine torque is greater than 50 N·m (68 lb ft).
    • TCC is commanded on.

Conditions for Setting the DTC

DTC P0751 sets if the following conditions occur two times.

Condition 1:

TCC slip speed is between 1,400-2,000 RPM for 0.9 seconds.

Condition 2:

TCC slip speed is between -1,000 to -100 RPM for 3.0 seconds.

Action Taken When the DTC Sets
    • The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.
    • The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.
    • The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

Conditions For Clearing the MIL/DTC
    • The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.
    • A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.
    • The scan tool clears the MIL/DTC.
    • The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

Diagnostic Aids
    • Verify that the transmission meets the specifications in the Shift Speeds table.
    • Other internal transmission failures may cause more than one shift to occur.

Refer to Shift Solenoid Valve State and Gear Ratio .

Test Description

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

  1. This step tests that the TCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.

DTC P0751 1-2/3-4 Valve Shift Solenoid Performance - No Second or Third Gear

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check ?

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Go to step 2

Go to DTC P1545 Air Conditioning (A/C) Clutch Relay Control Circuit in Engine Controls

2

  1. Install the Scan Tool .
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important: Before clearing the DTC, 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 ECM/TCM.

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

    6. Accelerate the vehicle, ensuring the TCM commands 1st, 2nd, 3rd and 4th gears.

Was a 1-1-4-4 shift pattern detected?

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Go to Step 3

Go to Diagnostic Aids

3
  1. Inspect the 1-2/3-4 shift circuit for the following conditions:
    2. • 1-2/3-4 Shift Solenoid Valve (1-2/3-4 SS Valve) mechanically stuck off.
    • Damaged 1-2/3-4 SS Valve O-ring.
    • 1-2 and 3-4 shift valve stuck in the released position.
  2. Repair the circuit. Refer to Transmission Overhaul in the 4L30-E Section of the Transmission Unit Repair.

Did you find and correct the condition?

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Go to Step 4

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4

Perform the following procedure in order to verify the repair:

  1. Clear DTCs.
  2. For condition 1, drive the vehicle in D and ensure the following conditions are met:
    3. • Throttle position is at least 10%.
    • TCM has commanded 2nd gear.
    • Engine speed is 1792-2304 RPM.
    • Transmission output speed is greater than 800 RPM.
    • Engine torque is greater than 50 N·m (68 lb ft).
    • TCC slip speed is 400-750 RPM for 1 second.
  3. For condition 2, drive the vehicle in D and ensure the following conditions are met:
    4. • Throttle position is at least 10%.
    • TCM has commanded 3rd gear.
    • Engine speed is 2016-2496 RPM.
    • Transmission output speed is greater than 1696 RPM.
    • Engine torque is greater than 50 N·m (68 lb ft).
    • TCC slip speed is -32 to +32 RPM for 3 seconds.

Did the transmission shift through all drive ranges as commanded by the TCM?

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System OK

Go to Step 1