COUPLING 3721142 - Caterpillar

The Electronic Control Module (ECM) will log a diagnostic code if the ECM detects all of the following conditions:
The engine has been running for three seconds, and the engine is not cranking.
The pattern of the timing ring is lost twice within three minutes without a ramp down in engine speed (rpm).
The pattern of the timing ring returns within one second of being lost.
Battery voltage is greater than 9 VDC for the last two seconds.The ECM will log a diagnostic code, and the ECM will have an active diagnostic code if the ECM detects all of the following conditions:
There is an invalid pattern for the timing ring for one second.
The secondary engine speed/timing sensor has a valid pattern for the timing ring.
The secondary engine speed/timing sensor has a signal that is greater than 100 rpm.
Battery voltage is greater than 9 VDC for the last two seconds.System Response:The ECM will log the diagnostic code. The ECM may have an active diagnostic code. The diagnostic code may be viewed on a display module or on the Caterpillar Electronic Technician (ET). If a valid signal is not received from the primary engine speed/timing sensor, the ECM will default to the secondary engine speed/timing sensor.Possible Performance Effect:
Engine misfires
Engine shutdownNote: The engine will shut down only if the primary engine speed/timing sensor and the secondary engine speed/timing sensor fail.Troubleshooting:Test Step 1. Results:
OK - STOP