Roadmaster 1992

Throttle Body Assembly

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Location



The TPS sensor is connected to the throttle shaft at the TBI unit.

Click image to see an enlarged view

Fig. TPS sensor-1991-1993

Operation



The Throttle Position Sensor (TPS) is a Linear Potentiometer that monitors the throttle position. The TPS operates within a 5 volt DC reference range, and provides a linear input signal to the Powertrain Control Module (PCM). The PCM uses data from the TPS to calculate air-fuel mixture, ignition timing, fuel injector pulse width, and transmission/transaxle gear position.

Removal & Installation



  1. Before servicing the vehicle, refer to the Precautions Section.
    NOTE
    Disconnecting the negative battery cable on some vehicles may interfere with the functions of the on-board computer systems and may require the computer to undergo a relearning process, once the negative battery cable is reconnected.


    NOTE
    If working near and/or around the SRS system and components, be sure to properly disable the SRS system. See disarming/arming the SRS system.

  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Disconnect the TPS electrical connector.
  6.  
  7. Remove the 2 mounting screws.
  8.  
  9. Remove the TPS and, if equipped, TPS seal from the throttle body.

    Click image to see an enlarged view

    Fig. TPS sensor-1991-1993



    Click image to see an enlarged view

    Fig. TBI unit and related components-1991-1993

  10.  

To install:


NOTE
Be sure to use new fasteners, as required.


NOTE
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 sealer are identified. 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.

  1. Place the TPS in position. Align the TPS lever with the TPS drive lever on the throttle body.
  2.  
  3. Install the 2 TPS mounting screws.
  4.  
  5. Connect the electrical connector.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. Using the GM diagnostic scan tool or aftermarket equivalent reprogram the necessary systems and components. Be sure to follow the scan tool manufacturer-s directions.
  10.  

Testing




NOTE
Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.

Connection & Wiring Diagnosis

Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.  

Many intermittent open or short circuits may be caused by wiring harness and connector movement due to vibration, engine torque, bumps and rough pavement, etc.

  1. Test the wiring harness and connectors by performing the following tests:

    Move the related connectors and wiring while monitoring the appropriate scan tool data.
     
    Move the related connectors and wiring with the component commanded ON and OFF. Using a suitable the scan tool, observe the component operation.
     
    With the engine running, move the related connectors and wiring while monitoring component operation.
     
    If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary.
     

  2.  
  3. Test the connector terminal pins and/or wiring by performing the following tests:

    Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body.
     
    Inspect for improperly formed or damaged terminals and test for incorrect terminal tension.
     
    Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body.
     
    Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and/or brittle sections of wire in the suspect circuits.
     
    Inspect for wires that are broken inside the insulation by gently pulling on suspect sections of wiring.
     

  4.  

Related Diagnostic Trouble Codes


Click image to see an enlarged view

Fig. Related Diagnostic Trouble Codes

Throttle Position Sensor

A properly operating TPS should display a linear -sweep- of the entire throttle range, and should not exhibit any voltage drop or signal break. If the feedback signal is not within the specified range, additional diagnosis is required in order to determine the proper function of the TPS, or if a fault exists in any related sub-systems.

Click image to see an enlarged view

Fig. Throttle Position Sensor Range Chart

Throttle Position Sensor Strategy

The TPS provides a linear input signal to the Powertrain Control Module (PCM), which is used to monitor the throttle position. The TPS monitors the entire range of throttle opening from 0.5 volts DC (0%) 4.5 volts DC (100%). In modern drive-by-wire throttle control systems, the TPS provides data to the PCM in order to calculate the desired throttle position, in addition to air-fuel mixture, ignition timing, fuel injector pulse width, and transmission/transaxle gear position.

The TPS utilizes positive coefficient logic: as the accelerator position is increased, the voltage is increased.

 
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