Edmunds Answers

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  • avatar 0patience 10/17/09 11:04 pm PST

    The shift solenoids are located on the valve body. Not sure, but they may be accessible from the outside of the valve body housing on your transmission.
    I would suspect that the 2 codes may be related, so I would concentrate on the TPS code first and try and solve it, then clear the codes, road test and recheck the codes.

    P0121
    CONDITIONS FOR RUNNING THE DTC
    No TP or Manifold Absolute Pressure (MAP) sensor DTCs set.
    Engine is running.
    MAP is below 50 kPa to check for a fixed high TP sensor input.
    MAP is above 70 kPa to check for a fixed low TP sensor input
    Idle Air Control (IAC) Position is between 0 and 130 counts.
    Throttle angle is steady.

    Check for the following conditions:
    Damaged or sticking throttle plate or IAC valve A throttle plate or IAC valve that allows too much airflow while the throttle should be closed may cause a high idle and DTC P0121 to be set. Refer to Idle Air Control System Check for diagnosis.
    Skewed MAP signal or malfunctioning MAP sensor An incorrect MAP signal may cause the PCM to incorrectly calculate the predicted TP sensor value during high engine load situations. Check for an unusually low MAP reading. This condition can cause DTC P0121 to be set.
    Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
    Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the Engine Coolant Temperature (ECT) display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction.


    P0753
    CONDITIONS FOR SETTING THE DTC
    The ignition is ON.
    The system voltage is 9-16 volts.
    The engine speed is greater than 500 RPM for 5 seconds, and not in fuel shut off.
    The PCM commands the solenoid ON and voltage remains high (B+).
    The PCM commands the solenoid OFF, and the voltage remains low (0 volts).
    All conditions are met for 5 seconds.
    Check for the following conditions:
    Inspect the wiring at the PCM, the transmission connector, 1-2 shift solenoid connector and all other circuit connecting points for the following conditions:
    A bent terminal
    A backed out terminal
    A damaged terminal
    Poor terminal tension
    A chafed wire
    A broken wire inside the insulation
    Moisture Intrusion
    Corrosion
    When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    Ensure that the scan tool commanded gear has correct solenoid states and ratio.


Answers

  • 0patience 10/17/09 10:00 pm PST

    I don't know what a PA is.

    But if you post the make, model and engine, along with the code NUMBERS, we can try help you sort it out.

    Use the Answer this Question button to reply.

  • brian1998 10/17/09 10:43 pm PST

    I have a 1998 Buick Park Avenue, 3.8, V-6 with 140,000 miles) ( The Check Engine Light came on) the codes that I am getting are PO121 (Throttle Position Sensor) and PO753 (Shift Solenoid). Do I need to replace both parts or see if first replacing the TPS will cure both malfunctions? Also where is the Shift Soenoid located Thanks, Brian

  • 0patience 10/17/09 11:04 pm PST

    The shift solenoids are located on the valve body. Not sure, but they may be accessible from the outside of the valve body housing on your transmission.
    I would suspect that the 2 codes may be related, so I would concentrate on the TPS code first and try and solve it, then clear the codes, road test and recheck the codes.

    P0121
    CONDITIONS FOR RUNNING THE DTC
    No TP or Manifold Absolute Pressure (MAP) sensor DTCs set.
    Engine is running.
    MAP is below 50 kPa to check for a fixed high TP sensor input.
    MAP is above 70 kPa to check for a fixed low TP sensor input
    Idle Air Control (IAC) Position is between 0 and 130 counts.
    Throttle angle is steady.

    Check for the following conditions:
    Damaged or sticking throttle plate or IAC valve A throttle plate or IAC valve that allows too much airflow while the throttle should be closed may cause a high idle and DTC P0121 to be set. Refer to Idle Air Control System Check for diagnosis.
    Skewed MAP signal or malfunctioning MAP sensor An incorrect MAP signal may cause the PCM to incorrectly calculate the predicted TP sensor value during high engine load situations. Check for an unusually low MAP reading. This condition can cause DTC P0121 to be set.
    Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
    Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the Engine Coolant Temperature (ECT) display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction.


    P0753
    CONDITIONS FOR SETTING THE DTC
    The ignition is ON.
    The system voltage is 9-16 volts.
    The engine speed is greater than 500 RPM for 5 seconds, and not in fuel shut off.
    The PCM commands the solenoid ON and voltage remains high (B+).
    The PCM commands the solenoid OFF, and the voltage remains low (0 volts).
    All conditions are met for 5 seconds.
    Check for the following conditions:
    Inspect the wiring at the PCM, the transmission connector, 1-2 shift solenoid connector and all other circuit connecting points for the following conditions:
    A bent terminal
    A backed out terminal
    A damaged terminal
    Poor terminal tension
    A chafed wire
    A broken wire inside the insulation
    Moisture Intrusion
    Corrosion
    When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    Ensure that the scan tool commanded gear has correct solenoid states and ratio.


  • brian1998 10/18/09 2:10 pm PST

    I purchased a new TPS and the manual said that I had to have the TPS adjusted at a repair garage? Is this the correct and what happens if I just replace the TPS without adjusting it? Thanks, Brian

  • 0patience 10/18/09 4:21 pm PST

    Why are you replacing the TPS? Did it test bad?
    Did you check all the other stuff I posted first?

    INSTALLATION PROCEDURE
    With the throttle valve in the normal closed position, install the TP sensor to the throttle body assembly.
    Apply thread-locking compound on the screws. Loctite 262 (R), GM Part No. 1052624, or equivalent should be used.
    Install the two TP sensor attaching screws.

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