Nissan 240SX/Altima 1993-1998 Repair Guide

Power Transistor

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TESTING



Two types of power transistors are used in these vehicles. One has a two-terminal connector, while the other has a three-terminal connector. Use the appropriate test when diagnosing the power transistor on your vehicle.

The 1445 240SX uses a two-terminal connector. However, it is tested using the three-terminal connector procedure. The third terminal needed for the test is located on the camshaft position sensor connector. Refer to the illustration for further information.

Two-Terminal Connector

See Figure 1



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Fig. Fig. 1: Check power transistor resistance between the terminals illustrated

Prior to testing the power transistor, perform a secondary spark test. If spark occurs at the spark plug, the power transistor is functioning properly.

  1. Turn the ignition OFF .
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Perform a visual inspection of the power transistor, and replace it if damaged.
  6.  
  7. Label and disconnect the two-terminal electrical harness from the transistor.
  8.  
  9. Label and disconnect the six-terminal electrical harness from the camshaft position sensor.
  10.  
  11. Inspect the harness connectors and transistor terminals for dirt, corrosion or damage. Repair as necessary.
  12.  
  13. Using an ohmmeter, check for resistance between the connector terminals as illustrated.
  14.  
  15. Resistance should always exist. If resistance is zero, the power transistor may be faulty.
  16.  
  17. Replace the power transistor as necessary.
  18.  

Three-Terminal Connector

See Figures 2, 3, 4, 5, 6, 7 and 8



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Fig. Fig. 2: The three-terminal power transistor is located on a bracket attached to the top of the air box



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Fig. Fig. 3: Check continuity between the terminals as illustrated and compare results with the diagnosis chart-three-terminal connector for all models except 1445 240SX



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Fig. Fig. 4: Check continuity between the terminals as illustrated and compare results with the diagnosis chart-three-terminal connector for a 1445 240SX



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Fig. Fig. 5: A reading such as that shown qualifies as a non-infinite/non-zero reading



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Fig. Fig. 6: In this hook-up, the ohmmeter is reading infinite



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Fig. Fig. 7: The digitial tester must have a diode check position and be able to measure up to 20 M(upside down U with little tails) to perform this inspection.



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Fig. Fig. 8: The digital tester must have a diode check position and be able to measure up to 20 M(upside down U with little tails) to perform this inspection.

Prior to testing the power transistor, perform a secondary spark test. If spark occurs at the spark plug, the power transistor is functioning properly.

  1. Turn the ignition OFF .
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Perform a visual inspection of the power transistor and replace if damaged.
  6.  
  7. Label and disconnect the electrical harness from the transistor.
  8.  
  9. Inspect the harness connector and transistor terminals for dirt, corrosion or damage. Repair as necessary.
  10.  
  11. Using an ohmmeter, check for continuity between the three terminals. Be sure to check all six probe/terminal combinations. Compare the results to the power transistor diagnosis chart.
  12.  

Ensure that the ohmmeter leads are connected properly. Since a diode is being tested, the positive and negative leads of the ohmmeter must be placed as directed by the chart. Failure to do so will result in incorrect readings.

  1. Replace the power transistor as necessary.
  2.  

REMOVAL & INSTALLATION



Two-Terminal Connector

The two-terminal connector power transistor is located inside the distributor and is not serviceable separately.

Three-Terminal Connector

See Figure 9



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Fig. Fig. 9: The three-terminal power transistor is attached to the bracket using two screws. The connector terminals are also visible in this illustration

  1. Disconnect the negative battery cable.
  2.  
  3. Label and disconnect the transistor electrical harness.
  4.  
  5. Remove the transistor mounting bolts.
  6.  
  7. Carefully remove the transistor.
  8.  

To install:
  1. Position the transistor and tighten the mounting bolts securely.
  2.  
  3. Connect the transistor electrical harness.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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