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Home >> Acura >> 1988 >> Legend Base, 2D Coupe, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Tests W/Codes >> Self-Diagnostic System >> Code 4 - CRK/CYL Sensor
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Code 4 - CRK/CYL Sensor

  1. Turn ignition off. Disconnect alternator sense fuse in under-hood relay box for 10 seconds to reset ECU. Start engine and observe "PGM-FI" warning light. If light is off, problem is intermittent. Test drive and check again.
  2. If light is on, turn engine off. Disconnect CRK/CYL sensor connector nearest the sensor. Measure resistance across Blue/Yellow and Blue/Green terminals at sensor. If reading is not 500-1000 ohms, replace sensor. If reading is within specification, proceed to next step.
  3. Check continuity between ground and sensor Blue/Yellow wire terminal. Check continuity between ground and sensor Blue/Green terminal. If continuity exists, sensor is shorted to ground. Replace sensor. If no continuity exists, proceed to next step.
  4. Reconnect sensor connector. Attach ECU test harness to right side wire harness side only. Measure resistance between ECU terminals B19 and B20. See Figure . Resistance should be 500-1000 ohms.
  5. If resistance is not within specification, repair open in Blue/Yellow and/or Blue/Green wire. If resistance is within specification, substitute a known good ECU. If condition is rectified, replace original ECU.
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