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

Camshaft Position Sensor

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OPERATION



See Figure 1



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Fig. Fig. 1: Camshaft sensor components and location-960 models

The function of the Camshaft Position (CMP) sensor is to tell the ECM if the camshaft is on the first or second revolution of an engine cycle. The CMP sensor allows the engine to determine which pistons are approaching TDC. The CMP sensor, in conjunction with the crankshaft position sensor, determine which cylinder requires ignition.

The CMP sensor consists of a trigger rotor and a Hall effect switch. The trigger rotor turns at the same speed as the camshaft. The ECM sends a 5-volt supply to the Hall effect sensor, which is grounded when the rotor passes the Hall effect switch, giving a zero voltage signal. When the sensor is shielded, the sensor returns the 5-volt signal to the ECM.

TESTING



See Figures 2, 3 and 4



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Fig. Fig. 2: CMP sensor connector terminals



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Fig. Fig. 3: Checking for battery voltage at terminal 3



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Fig. Fig. 4: Checking the signal return circuit of the CMP sensor

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the sensor connector.
  4.  
  5. To test the voltage lead:
    1. Using an voltmeter, measure the voltage at terminal 3. Turn the ignition ON , and measure the voltage between terminal 3 and ground.
    2.  
    3. Voltage should be battery voltage. If voltage is not present or out of range, repair the circuit. If voltage is ok, proceed to the next step.
    4.  

  6.  
  7. To test the signal return:
    1. Using an voltmeter, measure the voltage at terminal 2. Turn the ignition ON , and measure the voltage between terminal 2 and ground.
    2.  
    3. Voltage should be around 5v. If voltage is not present or out of range, repair the circuit. If voltage is ok, proceed to the next step.
    4.  

  8.  
  9. To test the ground circuit:
    1. Using an ohmmeter, measure the resistance at terminal 1. Turn the ignition ON , and measure the resistance between terminal 1 and ground.
    2.  
    3. Resistance should be 0 ohms. If continuity is not present or out of range, repair the circuit. If continuity is ok, replace the CMP sensor.
    4.  

  10.  

REMOVAL & INSTALLATION



See Figures 5, 6 and 7

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air inlet hose from the air cleaner housing and the throttle body.
  4.  
  5. Unplug the sensors connector.
  6.  
  7. Remove the two retaining screws and remove the sensor from the engine.
  8.  

To install:
  1. Install the sensor into place and tighten the retaining bolts.
  2.  
  3. Plug in the connector.
  4.  
  5. Install the air inlet hose onto the throttle body and the air cleaner housing.
  6.  
  7. Connect the negative battery cable.
  8.  



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Fig. Fig. 5: Crankshaft position sensor (1) and camshaft position sensor (2)



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Fig. Fig. 6: Removing the CMP sensor



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Fig. Fig. 7: Inspect the Hall effect switch inside the CMP sensor after removal

 
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