Volvo 240/740/760/780/940/960 1990-1998

Throttle Position Sensor

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OPERATION



The Throttle Position (TP) sensor is a potentiometer that provides a signal to the ECM that is directly proportional to the throttle plate position. The TP sensor is mounted on the side of the throttle body and is connected to the throttle plate shaft. The TP sensor monitors throttle plate movement and position, and transmits an appropriate electrical signal to the ECM. These signals are used by the ECM to adjust the air/fuel mixture, spark timing and EGR operation according to engine load at idle, part throttle, or full throttle. The TP sensor is not adjustable.

TESTING



See Figures 1, 2 and 3

  1. With the engine OFF and the ignition ON , check the voltage at the signal return circuit of the TP sensor by carefully backprobing the connector using a DVOM.
  2.  
  3. Voltage should be between 0.2 and 1.4 volts at idle.
  4.  
  5. Slowly move the throttle pulley to the wide open throttle (WOT) position and watch the voltage on the DVOM. The voltage should slowly rise to slightly less than 4.8v at Wide Open Throttle (WOT).
  6.  
  7. If no voltage is present, check the wiring harness for supply voltage (5.0v) and ground (0.3v or less), by referring to your corresponding wiring guide. If supply voltage and ground are present, but no output voltage from TP, replace the TP sensor. If supply voltage and ground do not meet specifications, make necessary repairs to the harness or ECM.
  8.  



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Fig. Fig. 1: Checking the signal return of the TP sensor



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Fig. Fig. 2: Checking the signal circuit of the TP sensor



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Fig. Fig. 3: Checking the ground circuit of the TP sensor

REMOVAL & INSTALLATION



See Figure 4

  1. Disconnect the negative battery cable.
  2.  
  3. Remove any components necessary to access the sensor.
  4.  
  5. Remove the connector from the sensor.
  6.  
  7. Remove the mounting screws from the sensor and remove the sensor.
  8.  

To install:
  1. Install the sensor onto the throttle plate shaft.
  2.  

The throttle plate shaft is designed to fit a specific way on the sensor, note the position of the shaft before tightening the bolts.

  1. Tighten the mounting screws.
  2.  
  3. Install the sensor connector.
  4.  
  5. Install any components removed to access the sensor.
  6.  
  7. Connect the negative battery cable.
  8.  



Click image to see an enlarged view

Fig. Fig. 4: Location of the TP sensor on the throttle body

 
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