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DTC P0720/Flash Code 9: Countershaft Speed Sensor

  1. Ensure countershaft speed sensor is properly installed. Reinstall sensor and recheck operation. If sensor is properly installed, go to next step.
  2. Turn ignition off. Disconnect countershaft speed sensor harness connector. Check resistance between sensor terminals. If resistance is 400-600 ohms, go to next step. If resistance is not 400-600 ohms, replace countershaft speed sensor.
  3. Disconnect 26-pin PCM harness connector "E". Check continuity between chassis ground and PCM harness connector "E" terminals No. 5 (Blue wire), then No. 18 (Green wire). See Figure . If continuity does not exist, go to next step. If continuity exists, repair short in circuit between PCM harness connector "E" terminals No. 5 and No. 18, and countershaft speed sensor. See WIRING DIAGRAMS  .
  4. Reconnect countershaft speed sensor harness connector. Check resistance between PCM harness connector terminals No. 5 (Blue wire) and No. 18 (Green wire). If resistance is 400-600 ohms, go to next step. If resistance is not 400-600 ohms, repair loose terminal or open in circuit between PCM harness connector terminals No. 5 and No. 18 and countershaft speed sensor.
  5. Check for loose PCM harness connectors. Repair as necessary. If connectors are okay, substitute with a known-good PCM and recheck system. If symptom or problem goes away, replace original PCM.
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