New Holland ENG 3657 – Engine ECU: CAN Bus Communication: Timed Out Error of CAN-Receive-Frame CM1BC

Communication breakdown on the machine's Controller Area Network (CAN) bus. Specifically, the Engine Control Unit (ECU) did not receive the expected "CM1BC" message frame from the main communication system within the allotted time limit.

• L216
• L220
• L228
• C-Series
• T5
• T6
• T7
• T8
• TM
• TS
• FR450
• FR500
• FR600
• CR Series
• CX Series

1. 1

   Confirm stable battery voltage and inspect main ground straps. Low voltage or poor grounds can cause modules to drop off the network.

2. 2

   Perform a CAN Bus Resistance Test: With the battery disconnected, measure the resistance between the CAN HI (yellow) and CAN LO (green) wires at the diagnostic port. Total resistance should read exactly 60 ohms. If it reads 120 ohms: One of the terminating resistors is missing, failed, or there is an open circuit in the wiring leading to it.

3. 3

   Inspect the wiring looms at high-movement points (seat area, steering column, cab pivot, loader brackets) for chafing, pinching, or bare wires.

4. 4

   Check the main ECU and CAN bus connectors for moisture, corrosion, or pushed-out pins.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Locate the Break

   If your resistance test yielded 120 ohms, trace the CAN bus harness to locate the two terminating resistors (usually located at the extreme ends of the harness, sometimes behind the cab cover or in the engine bay).

3. 3

   Test the Resistors

   Unplug the terminating resistors and test them individually. They should each read 120 ohms. If one reads open (infinite resistance) or is physically damaged, it must be replaced.

4. 4

   Repair Wiring

   If the resistors are good, trace the CAN HI and CAN LO wires for breaks or shorts to ground. If a wire is broken, splice in a repair section. Note: It is critical that the wire lengths are not significantly altered from the original, as this will affect the data transmission performance of the CAN bus.

5. 5

   Clean Connectors

   Dry any moisture found in the connectors and apply a light coat of dielectric grease to prevent future water ingress.

6. 6

   Clear Codes

   Reconnect the battery. Use the New Holland Electronic Service Tool (EST) or a compatible J1939 CAN reader to clear the inactive fault codes from the ECU memory.

7. 7

   Retest

   Cycle the key and run the machine to verify the CM1BC timeout code does not return.