Testing Multiple Modules Not Communicating On A Can Bus
CAN Bus networks may contain the following:
- Greater than 12 different CAN Bus networks may be present.
- Certain ECUs can be connected to multiple CAN Bus networks.
- Some CAN Bus networks may be equipped with one or more Splice Block connectors.
CAN BUS DIAGNOSTICS:
The 12-volt Main Battery, and Auxiliary Battery (if equipped), MUST be disconnected before measuring the resistance on a CAN Bus.
The Scan Tool Topology can assist in diagnosing a CAN Bus network failure, but the Scan Tool Topology MAY NOT display the actual CAN Bus module/network layout.
If the suspected CAN Bus is equipped with one or more Splice Block connectors, proceed to the TESTING WITH THE MOPAR® DIAGNOSTIC SPLICE BLOCK KIT procedure below.
- DETERMINE WHICH CAN BUS IS FAULTED
- Go To 2
- USING THE SCAN TOOL CHECK FOR COMMUNICATION WITH THE SGW MODULE
Does the scan tool communicate properly with the SGW Module?
- Yes - Go To 3
- No - Perform the SCAN TOOL WILL NOT COMMUNICATE WITH VEHICLE diagnostic procedure. Refer to SCAN TOOL WILL NOT COMMUNICATE WITH VEHICLE .
- USING THE SCAN TOOL CHECK FOR COMMUNICATION WITH THE POWERTRAIN CONTROL MODULE (PCM)
Is the VIN (Vehicle Identification Number) and engine description displayed on the scan tool?
- Yes - Go To 4
- No - Perform the NO RESPONSE FROM ECU diagnostic procedure. Refer to NO RESPONSE FROM ECU .
- USING THE SCAN TOOL TOPOLOGY CHECK THE CAN BUS COMMUNICATION
Does the scan tool communicate with any of the ECUs on the faulted CAN bus?
- Yes - This indicates the CAN bus is operational. Perform the COMMUNICATION DIAGNOSTIC PROCEDURE. Refer to COMMUNICATION DIAGNOSTIC PROCEDURE .
- No - Go To 5
- MEASURE THE VOLTAGE ON THE FAULTED CAN BUS
Compare the measured voltage to the above CAN BUS VOLTAGES table and select the matching condition below.
- The CAN Bus voltage is normal - Go To 7
- The CAN Bus voltage is above or below normal - Go To 6
- SELECT THE VOLTAGE MEASURED ON THE FAULTED CAN BUS
Is the voltage on the faulted CAN Bus above or below the typical CAN Bus voltages?
- Voltage is Above - Isolate and repair the faulted CAN Bus circuit for a short to voltage.
- Voltage is Below - Go To 7
- DISCONNECT THE 12-VOLT BATTERIES AND MEASURE THE RESISTANCE OF THE FAULTED CAN BUS
Compare the measured resistance to the above CAN BUS TERMINATION RESISTOR RESISTANCES table and select the matching condition below.
NOTE:A CAN Bus with an open termination resistor will measure approximately 120.0 ohms.
- Resistance is Normal - Go To 9
- Resistance is Above or Below Normal - Go To 8
- SELECT THE RESISTANCE MEASURED ON THE FAULTED CAN BUS
Is the resistance on the faulted CAN Bus above or below the normal CAN Bus termination resistor resistance?
- Resistance is Above Normal - Isolate and repair the faulted CAN Bus circuit for an open or high resistance.
- Resistance is Below Normal - Isolate and repair the faulted CAN Bus circuit for a short to ground.
- FURTHER ISOLATION OF THE FAULTED CAN BUS IS NEEDED
- Connect the 12-volt batteries.
- Using the scan tool topology disconnect each ECU on the faulted CAN Bus, one at a time, until CAN bus communication returns to normal operation.
- Replace the ECU that, when disconnected, allows normal CAN Bus operation.