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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1996 🢒 Fleetwood 🢒 DTC 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance

Object Number: 42270 Size: MF
OBD II Symbol Description Notice

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 in two ignition cycles, then DTC P0751 sets. The pattern that the PCM detects depends on the mechanical failure. DTC P0751 is a type B DTC.

Conditions for Setting the DTC
    • No TP DTCs P0122 or P0123
    • No VSS DTC P0502
    • No TCC Stuck ON DTC P0742
    • No 1-2 SS Valve DTC P0753
    • No 2-3 SS Valve DTC P0758
    • No TFP Val Position Sw DTC P1810
    • No 3-2 Shift Solenoid Valve Assembly DTC P1886
    • The gear range is D4.
    • The vehicle speed is greater than 8 km/h (5 mph).
    • The transmission fluid temperature is 20-130°C (68-266°F).
    • The traction control is not active.
    • All the above conditions have been met and the combination of Conditions 1,2,3, and 4 or 1,2,3, and 5 occur two consecutive times.

Condition 1

       - Commanded 1-2 shift
       - The TP angle is 17-42%.
       - The TP angle is constant within +/-3%.
       - Vehicle speed is 8-48 km/h (5-30 mph).
       - Within 2.5 seconds, the engine speed in 2nd gear must be 150 RPM greater than the last speed in 1st gear.

Condition 2

       - Commanded 2-3 shift
       - The TP angle is 17-32%.
       - The TP angle is constant within +/-5%.
       - Vehicle speed is 32-72 km/h (20-45 mph).
       - Within 1.7 seconds, the engine speed in 3rd gear must be 75 RPM less than the last speed in 2nd gear.

Condition 3

       - Commanded 3-4 shift
       - The TP angle is 17-30%.
       - The TP angle is constant within +/-3%.
       - The vehicle speed is 45-105 km/h (28-65 mph).
       - Within 3 seconds, the engine speed in 4th gear must be 20 RPM greater than the last speed in 3rd gear.

Condition 4

       - Commanded 4th gear
       - The TCC is ON.
       - The TP angle is 13-26%.
       - The speed ratio is 0.85-1.2 (the speed ratio is the engine speed ÷ the output speed).
       - The TCC slip speed is 300-2000 RPM for greater than 4 seconds.

Condition 5

       - Commanded 4th gear
       - The TCC is ON.
       - The TP is 13-26%.
       - The Speed ratio is 0.5-0.788 (the speed ratio is the engine speed ÷ the output speed).
       - The TCC slip speed is -20 to +20 RPM for greater than 4 seconds.

Action Taken When the DTC Sets
    • The PCM commands maximum line pressure.
    • The PCM freezes shift adapts from being updated.
    • 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.

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

    2.

  2. This step verifies that the following sequence occurs:

    3. • 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

No

1

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

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check , Section 6.

2

  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 for reference. The Clear Info function will erase the data.

  3. Record the DTC Freeze Frame and Failure Records.
  4. While the engine is operating, apply the brake pedal.

    5. 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 Transmission Fluid Pressure Manual Valve Position Switch Resistance Check

3

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

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

--

Go to Step 4

Go to Diagnostic Aids

4
    • 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?

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Go to Step 5

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5
  1. After the repair is complete, select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions (only if the traffic and road conditions permit):
    4. • Hold the throttle at 20% and accelerate to 88 km/h (55 mph). If the throttle moves more than 3%, stop the vehicle and start over.
    • Drive at 88 km/h (55 mph) for 3 km (2 miles).
  4. Select Specific DTC and enter DTC P0751.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1