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CAN Communication Line Inspection

■ Inspection procedure for resistance measurement 

When measuring resistance, it is generally necessary to disconnect the circuit being tested from the power supply before hand. The vehicle's battery should therefore be disconnected and wait about four minutes to allow all capacitors in the system to discharge.

Inspection procedure for resistance test:

  1. The CAN bus must be disconnected from the power supply.
  2. The measurement is taken between the CAN High and CAN Low leads.
  3. The measurement recorded may differ from the specified levels by a few ohms.

■ Resistance measurement with matching resistor 

  1. Ignition "OFF" and disconnect the battery and wait about four minutes.
  2. Make sure all modules are properly connected.
  3. Measure resistance between Pin No. 3 (C-CAN High) and Pin No. 11 (C-CAN Low) terminal of Data Link Connector harness connector.

    Specification:  Approx. 60 Ω

  4. Is the measured value within specification?

    YES 

    • Go to next procedure.

    NO 

    • If the value is out of specification then, go to "CAN Resistor Inspection" procedure.

      * If the measured value is approx. 0Ω, then check for short CAN communication line.

      * If the measured value is approx. ∞Ω, then check for open CAN communication line.

■ CAN Resistor Inspection 

  1. Ignition "OFF"
  2. Disconnect battery (-) cable.
  3. Refer to REMOVAL BCM And: REMOVAL 1.6LT, REMOVAL 2.0L GDI, or REMOVAL 2.0 MPI NU and disconnect BCM and ECM/PCM connector.
  4. Measure the resistance between Pin No. 85 (C-CAN High) and Pin No. 63 (C-CAN Low) terminal of ECM.(2.0 GDI M/T, 1.6 T-GDI)
  5. Measure the resistance between Pin No. 60 (C-CAN High) and Pin No. 77 (C-CAN Low) terminal of PCM.(2.0 GDI A/T)
  6. Measure the resistance between Pin No. 77 (C-CAN High) and Pin No. 60 (C-CAN Low) terminal of PCM.(2.0 MPI)
  7. Measure the resistance between Pin No. 13 (C-CAN High) and Pin No. 12 (C-CAN Low) terminal of BCM.

    Specification:  Approx. 120Ω

  8. Is the measured value within specification?

    YES 

    • Go to next procedure.

    NO 

    • Carefully re-do this troubleshooting guide steps.
    • If no problems were found with the circuits or connectors, replace ECM/PCM or Instrument Cluster and then go to "Verification of Vehicle Repair " procedure.

■ CAN Signal Inspection 

  1. Ignition "OFF"
  2. Connect VMI to KDS/GDS and launch the oscilloscope (2 Channel):

    Channel A (+): Pin No. 3 (C-CAN High) terminal (DLC connector)

    Channel A (-): Ground

    Channel B (+): Pin No. 11 (C-CAN Low) terminal (DLC connector)

    Channel B (-): Ground

  3. Ignition "ON"

    Specification:  C-CAN High voltage - Approx. 2.8V/C-CAN Low voltage - Approx. 2.2V (Average)

    Fig 1: Scantool Display - Normal C-CAN Signal Waveform
    G12160310Courtesy of KIA MOTORS AMERICA, INC.
  4. Is the measured value within specification?

    YES 

    • Fault might be intermittent and caused either by poor contact in connectors or wiring harness, or it has been repaired and control module memory is not cleared yet. Thoroughly check terminal of battery, all connectors (and connections) for looseness, bending, corrosion, contamination, deterioration, and/or damage.
    • Repair or replace as necessary and then go to "Verification of Vehicle Repair " procedure.

    NO 

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