No Start | U1000 CAN Communication Circuit

🚗 2006 Nissan Frontier

• Customer bought a car with a broken ignition switch (by thieves).
• He replaced the ignition switch with a key, but car didn’t start. Multiple other modules have been replaced since then to rectify the issue.
• Customer managed to start the car by hot wiring a starter relay circuit. At this point he brought it to me.
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🩺 Diagnosis

• Scanned the vehicle
  • Scanner retrieved “U1000 CAN Communication Circuit” codes from most of the modules that communicated.
  • Some modules didn’t communicate.
• Diagram
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• Checked the voltages on OBDII plug pins 6 and 14 with a multimeter.
  • Found suspiciously high delta V on both the CAN-Low and CAN-High (1V to 4V).
• Pulled out an oscilloscope to look a little deeper into CAN Bus activity
  • Note that blue and red waveforms should mirror each other, but instead I saw this. There is quite a noticeable difference in dV and extra noise on a blue channel
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• Started unplugging control modules to see if i can narrow down my search of a failed component.
  • After unplugging IPDM, waveform became noticeably cleaner
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  • But CAN communication issue didn’t go away. U1000 still remained in other modules.
• Testing continuity of CAN wires revealed one line open (pink wire).
• Tracing the wire found a spot were something like a grinder cut into a wiring harness and cut some wires.
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• Connected the wires back together. Car started right up. No codes.
• Scanned the CAN lines again for comparison.
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