666: Canbus Failure - Engine Controller

1. Remove the cover of right side console to gain access to the fuse/relay panel. Verify fuse 18 in the cab fuse panel is not defective.

A. If the fuse is good. Using a multimeter verify with the key positioned to the ON/RUN position 12v on both sides of the 5 amp fuse.

B. If no 12v is found at fuse 18, check for 12v IGN power out of key switch on the blue 16g wire. Replace key switch if necessary.

C. If 12v is found at the blue wire on the key switch, then repair or replace the cab harness.

2. After verifying that the fuse 18 is good and the fuse has the correct voltage, proceed to the rear of the machine and open the rear door covering the radiator. Below the radiator and just to the right of the battery is a black box. Remove the cover off the box. Inside this compartment locate the inline 30 amp fuse holder. This is a black fuse holder with two, red 12g wires going into it.

A. After locating the inline fuse holder. Verify the 30 amp fuse is not defective and that the fuse holder is not corroded.

B. If the fuse is good and there is no corrosion. Verify 12v on bolt sides of the 30 amp fuse.

3. If the problem still exists, proceed to the right side engine door of the machine and open the right side engine door. Locate the ECU ground wires bolted directly to the engine block just in front of and behind the water separator. The grounds consist of two 10g & one 12g black wires. Verify wiring is tight and free of corrosion.

4. If the problem still exists, proceed to the right side engine door of the machine and open the right side engine door. Locate the engine control module (ECM) bolted to the frame behind the engine bell housing.

5. Locate the J2 connector on the ECM and unplug the J2 connector. With the keyswitch positioned to the ON/RUN position verify 12v on pins 1, 5, 25, 26, 27 and 28.

A. If there is no 12v on pins 1, 25, 26, 27 and 28 then a continuity test will need performed between the pins and the inline 30 amp fuse.

B. If there is no continuity, repair or replace the chassis harness.

C. If there is no 12v on pin 5 then a continuity test will need performed between the pin 5 and the fuse 18 in the fuse block in the cab. If the continuity test fails then the chassis and cab harnesses will need tested separately to determine which harness will need repaired or replaced.

Note: When testing each harness locate the engine bulk 2 connector in the cab. The connector is located just below the fuse block in the right hand console under the controller.

6. After locating the connector disconnect the connector and locate pin B1 in the (socket side) of the connector. Perform a continuity test between B1 and pin 5 on the ECM J2 connector. If the continuity test passes then test the cab harness. If the continuity test fails repair or replace the chassis harness.

To test the cab harness locate pin B1 on the (pin side) of the connector. Perform a continuity test between the B1 pin and fuse 18 in the fuse block.

7. Repair or replace harness if the continuity test fails.

8. After testing the power side and all of the tests have passed. Then the ground circuit to the ECM will need to be tested. Locate the J2 connector on the ECM. Unplug the J2 connector. Turn the keyswitch to the OFF position and verify continuity to battery ground on the ground pins 49, 50, 51, 52 and 73. If there is no continuity then repair or replace the chassis harness.

9. If all of the power and ground tests have passed. Contact your local Cummins dealer for further assistance.