Hello, This is a tough question to answer , The p1689 fault indicates that a communication problem exist between the cummins controller and the injection pump module . The crank sensor faults can be set when the communications is lost or the crank sensor circuits are causing the communications loss. First thing I would do is to swap the fuel control relays in the underhood fuse box with a different one . A poor relay can cause the 1689 fault . I would inspect the wiring for rub thorough , shorts or loose connections. You could have a broken wire or poor connections at the crank sensor or the cummins controller. Be careful when testing the connectors for the fuel injection pump and computers. These connectors can not be replaced because there are no parts availible. If damage to those connectors is found the engine wiring harness would have to be replaced.
If you - when you take it to the dealer , try to find the largest one in your area, They will likely have guys that do diesels only.
If you need more info please reply, Thanks Scott.
Hello, The crank sensor circuit,
You can test for 5 volts at the cranks sensor, test for ground and continuity on the signal wire. If you have a scan tool that will access the cummins controller, you can jump the 5 volt supply to the signal wire and there should be a reading seen as a rpm change on the scanner.
If the touching together the signal and 5 volt wire does not cause an RPM change . I would make a 3 wire jumper harness and rewire the sensor to the ecm . this would eleminate the possible wire harness failure. The ECM is very robust and does not fail often at all. Most dealer diesel techs will have a test unit they install for tests.