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Ken
Ken, ASE Certified Technician
Category: Chevy
Satisfied Customers: 754
Experience:  GM Certified Technician, 25 Years Automotive Experience
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2005 Chevy malibu: diagnostic..position sensor..throttle body..TPS

Customer Question

2005 Chevy malibu 2.2L,,diagnostic says throtlle position sensor bad,, I've looked at throttle body and see metal cover on right side and I believe TPS is inside it,,,? is how does it come off there are no screws. I already have the part, But also is this something you can or even should do in your driveway?
Submitted: 4 years ago.
Category: Chevy
Expert:  Ken replied 4 years ago.
Hi and thanks for your question! The TPS on that motor is part of the throttle body and is not serviced. You have to get a hole throttle body. They must have sold you the wrong TPS. I have never seen parts for the Electronic throttle body. The older 2.2L had a TPS, but not that one. Thank You Ken
Throttle Body Assembly Replacement

Removal Procedure

Notice: Do not use solvent of any type when cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as damage to the gasket surfaces and throttle body assembly may result.

Use care in cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as sharp tools may damage the gasket surfaces.

 

 

Notice: Do not use any solvent that contains Methyl Ethyl Ketone (MEK). This solvent may damage fuel system components.

  1. Remove the air cleaner resonator.
  2. Disconnect the throttle body harness connector.

  3. Object Number:(NNN) NNN-NNNN Size: SH

  4. Remove the throttle body attaching bolts.
  5. Remove the throttle body from the intake manifold.

Installation Procedure


    Object Number:(NNN) NNN-NNNN Size: SH

  1. Inspect the throttle body gasket and replace if necessary.
  2. Install the throttle body to the intake manifold.
  3. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  4. Install the throttle body attaching bolts.
  5. Tighten
    Tighten the throttle body attaching bolts to 10 N·m (89 lb in).

  6. Connect the throttle body harness connector.
  7. Install the air cleaner resonator
Expert:  Ken replied 4 years ago.

Throttle Actuator Control (TAC) System Description

Purpose

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:

Accelerator pedal position (APP) sensing
Throttle positioning to meet driver and engine demands
Throttle position (TP) sensing
Internal diagnostics
Cruise control functions
Manage TAC electrical power consumption

The TAC system includes the following components:

The APP sensors
The throttle body assembly
The powertrain control module (PCM)

Accelerator Pedal Position (APP) Sensor

The accelerator pedal contains 2 individual accelerator pedal position (APP) sensors within the assembly. The APP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:

A 5-volt reference circuit
A low reference circuit
A signal circuit

The APP sensors are used to determine the pedal angle. The powertrain control module (PCM) provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors provide the PCM with signal voltage proportional to the pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.

Throttle Body Assembly

The throttle assembly contains the following components:

The throttle blade
The throttle actuator motor
The throttle position (TP) sensor 1 and 2

The throttle body functions similar to a conventional throttle body with the following exceptions:

An electric motor opens and closes the throttle valve.
The throttle blade is spring loaded in both directions and the default position is slightly open.
There are 2 individual TP sensors within the throttle body assembly.

The TP sensors are used to determine the throttle plate angle. The TP sensors provide the powertrain control module (PCM) with a signal voltage proportional to throttle plate movement. The TP sensor 1 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. The TP sensor 2 signal voltage at closed throttle is near the low reference and increases as the throttle plate is opened.

Powertrain Control Module

The powertrain control module (PCM) is the control center for the throttle actuator control (TAC) system. The PCM determines the drivers intent and then calculates the appropriate throttle response. The PCM achieves throttle positioning by providing a pulse width modulated voltage to the TAC motor.

Modes of Operation

Normal Mode

During the operation of the throttle actuator control (TAC) system, several modes or functions are considered normal. The following modes may be entered during normal operation:

Minimum pedal value--At key-up the powertrain control module (PCM) updates the learned minimum pedal value.
Minimum throttle position (TP) values--At key-up the PCM updates the learned minimum TP value. In order to learn the minimum TP value, the throttle blade is moved to the closed position.
Ice break mode--If the throttle is not able to reach a predetermined minimum TP, the ice break mode is entered. During the ice break mode, the PCM commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
Battery saver mode--After a predetermined time without engine RPM, the PCM commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.

Reduced Engine Power Mode

When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:

Acceleration limiting--The PCM will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
Limited throttle mode--The PCM will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
Throttle default mode--The PCM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
Forced idle mode--The PCM will perform the following actions:
- Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned OFF.
- Ignore the accelerator pedal input.
Engine shutdown mode--The PCM will disable fuel and de-energize the throttle actuator.

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