PULLEY GP-FAN & ALT DRIVE 2622027 - Caterpillar

Unwanted Engine Shutdown Caused By "01" Diagnostic
There have been reports of unwanted generator set shutdowns with a "01" diagnostic display on the Engine Control Module (ECM). According to the Service Manual, a "01" diagnostic display indicates that there is no signal to the ECM from the magnetic speed sensor.
There are two methods the ECM determines a lack of speed signal input. The first method is by leaking a very small amount of current through the sensor to detect continuity. Step 1, of Problem 1 in the EMCP Service Manuals, outlines the method to troubleshoot the sensor for continuity problems. This is a valid and useful step which can be used to determine the integrity of the sensor wiring.
Step 2 relates to the lack of a signal incoming to the ECM due to problems other than lack of continuity. The diagnosis of the problem in this step assumes that the fault lies in either the speed sensor, the ECM, or an incorrect air gap setting on the sensor. In fact, there are a number of problems which can cause a "01" diagnostic, and the present troubleshooting procedure can lead a service person to replace an ECM that is not faulty.
The following is the second method by which a "01" diagnostic is declared. After the ECM determines that continuity is present and after the starter motor relay in the ECM is energized to start the generator set, the ECM begins looking for a frequency signal from the magnetic pickup. If no signal is present, then the ECM declares a "01" diagnostic. The generator set is shutdown and cannot be started until the "01" diagnostic is cleared and the air shutoff (if provided) is reset. The fallacy in this diagnostic process is that the ECM assumes that no problems exist in the starting system, when in reality, any number of problems could exist in the starting system which would result in a "01" diagnostic. A list of known problems which can cause the "01" diagnostic follows: 1. Failed starter motor or starter motor pinion solenoid.2. Failed circuit breaker (CB2).3. Failed starter motor mag switch (SMMSI or SMMS2).4. Butt engagement of the starter pinion with the flywheel ring gear.5. Blown fuse on the ECM starter motor relay output.6. Faulty wiring anywhere in the starting system components. In addition, for generator sets with and optional prelube pump:
7. Failed prelube pump.8. Failed prelube pump mag switch.9. Failed prelube pump pressure switch.
When conducting Step 2 of Problem 1 in the Service Manual, check for all of the above listed problems before making a decision that the ECM is faulty. Note that this pertains only to Test Results and Diagnosis Part A of Problem 1, Step 2. Make note of this information in the appropriate location in the References. The Test Results and Diagnosis Part B of Problem 1, Step 2 (test of output voltage from sensor) is still valid.
Unwanted Engine Shutdown Caused By "04" Diagnostic
There have been reports of unwanted generator set shutdowns with