Case IH 19403 – Engine Control Module (ECM) or Vehicle Control Module (VCM): Timeout of CAN-Transmit-Frame Vehicle Power Message, VEP1, comTx_VehPow

A Controller Area Network (CAN) bus communication error where the receiving module expected to see the VEP1 (Vehicle Electrical Power 1) message on the CAN bus but did not receive it within the programmed time limit. This indicates either a physical wiring issue on the CAN bus, a failure of the module responsible for transmitting the message, or a loss of power to the transmitting module.

• Tier 4b
• Puma
• Optum
• Magnum
• Steiger
• 580N
• 590SN

1. 1

   Check for accompanying CAN timeout codes (e.g., 19400, 19402, 19404) to determine if there is a global CAN bus failure rather than an isolated VEP1 issue

2. 2

   Verify the charging system by measuring battery voltage (approx. 12.6V resting) and alternator output (approx. 14.2V running) to ensure modules are not dropping off the CAN bus due to low voltage

3. 3

   Perform a CAN Bus Resistance Test at the diagnostic connector with the key OFF and battery disconnected (should read exactly 60 ohms; 120 ohms indicates an open circuit/missing resistor, 0 ohms indicates a short)

4. 4

   Visually inspect the CAN wiring harness between the ECM and the cab/body controller for chafing, rodent damage, or melted insulation

1. 1

   Disconnect Power

   Turn off the master disconnect switch or remove the negative battery cable to prevent electrical spikes.

2. 2

   Inspect Connectors

   Locate the main harness connectors at the ECM and the Cab/Body controller. Disconnect them and inspect the pins for pushed-out terminals, moisture, or green corrosion.

3. 3

   Clean and Reseat

   Clean any suspect pins with electrical contact cleaner, apply a light amount of dielectric grease, and firmly reseat the connectors.

4. 4

   Repair Wiring

   If the CAN resistance test failed, trace the CAN High (usually yellow) and CAN Low (usually green) wires. Repair any breaks or shorts using OEM-approved twisted-pair splicing methods (maintaining the twist as close to the splice as possible).

5. 5

   Check Terminating Resistors

   If a terminating resistor is found to be burnt or physically damaged, replace it.

6. 6

   Clear Codes and Retest

   Reconnect the battery. Connect the CNH Electronic Service Tool (EST) to clear the inactive 19403 code. Start the machine and monitor the J1939 data list to verify that the VEP1 (Battery Voltage) parameter is actively updating and the code does not return.