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Home >> Jeep >> 1990 >> Wagoneer >> Repair and Diagnosis >> Engine Performance >> System >> Ignition System Tests - 4.0L >> Testing >> Knock Sensor Test
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Knock Sensor Test

  1. Connect Diagnostic Tester M.S. 1700 to the vehicle.
  2. Go to "State Display" mode.
  3. Start the engine and let idle.
  4. Observe knock sensor value.
  5. Using the tip of a screwdriver, lightly tap the cylinder block near the sensor while observing the knock sensor value.
  6. The knock sensor value should increase when the cylinder block is tapped.
  7. If the knock sensor value does not increase while tapping on the cylinder block near the knock sensor, check for proper connections to the knock sensor. If connections are good, replace the knock sensor. Refer to REMOVAL & INSTALLATION in this article.
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