CAN Communication Line Inspection

■ Inspection procedure for impedance 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 (DLC).

   Specification:  Approx. 60 Ω

4. Is measured value within specification?

   YES 

   • Check each module connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair " procedure.

   NO 

   • If the measured value is out of specification, go to "CAN resistor inspection" procedure below.

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

     *If the measured value is approx. 120 Ω, then check for open CAN communication line of control module with resistor.

■ CAN resistor inspection (Theta-II 2.0 TGDI, Theta-II 2.4 GDI, Gamma 1.6 TGDI) 

1. Ignition "OFF".
2. Disconnect battery (-) cable.
3. Refer to INSTRUMENT CLUSTER and ENGINE CONTROL MODULE (ECM) (1.6L) , ENGINE CONTROL MODULE (ECM) (2.0L) or ENGINE CONTROL MODULE (ECM) (2.4L) and disconnect Instrument Cluster and PCM/ECM connector.
4. Measure the resistance between Pin No. 32 (C-CAN High) terminal and Pin No. 33 (C-CAN Low) terminal of Instrument Cluster.
5. Measure the resistance between Pin No. 77 (C-CAN High) terminal and Pin No. 60 (C-CAN Low) terminal of PCM. (Theta-II 2.0 TGDI, Theta-II 2.4 GDI)
6. Measure the resistance between Pin No. 85 (C-CAN High) terminal and Pin No. 63 (C-CAN Low) terminal of ECM. (Gamma 1.6 TGDI)

   Specification:  Approx. 120 Ω

7. Is the measured value within specification?

   YES 

   • Go to "CAN Signal Inspection" procedure below.

   NO 

   • Carefully re-do this troubleshooting guide steps.
   • If problem still occurs, replace PCM/ECM or Instrument Cluster whichever has faulty resistor and then go to "Verification of Vehicle Repair "

■ 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 (Data Link Connector)

   Channel A (-): Ground

   Channel B (+): Pin No. 11 (C-CAN Low) terminal (Data Link Connector)

   Channel B (-): Ground

3. Ignition "ON"

   Specification:  C-CAN High voltage - Approx. 2.8V/C-CAN Low voltage - Approx. 2.1V (Average)

   Fig 1: Screen Display - Normal C-CAN Signal Waveform

   Courtesy 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 

   • Repair open or short in C-CAN communication line and then, go to "Verification of Vehicle Repair " procedure.
   • If problem keep occurs, go to "Component Inspection " procedure.