WHEEL 2G5747 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with either of the engine speed/timing sensors. Also, use this procedure to troubleshoot the electrical system if any of the diagnostic codes in Table 1 are active or easily repeated.
Table 1
Diagnostic Trouble Codes
J1939 Code and Description Conditions that Generate the Code System Response
190-8 Engine Speed : Abnormal Frequency, Pulse Width, or Period The signal from the primary engine speed/timing sensor is intermittent or the signal has been lost. The engine will use the signal from the secondary engine speed/timing sensor for engine speed/timing.
The code is logged.
637-13 Engine Timing Sensor : Out of Calibration the engine has failed the automatic timing calibration during engine start-up The value of the timing offset that has been stored in memory will be used. This value will continue to be used for the timing calibration until the diagnostic is resolved
The code is logged.
723-8 Engine Speed Sensor #2 : Abnormal Frequency, Pulse Width, or Period The signal from the secondary engine speed/timing sensor is intermittent or the signal has been lost. The engine will use the signal from the primary engine speed/timing sensor for engine speed/timing.
The code is logged. The engine uses two engine speed/timing sensors. The primary speed/timing sensor detects the reference for engine speed and timing from a timing ring on the crankshaft timing gear. The timing ring consists of a notched pattern that is machined onto a portion of the gear. The signal from the primary engine speed/timing sensor is also used by the Electronic Control Module (ECM) as a control reference during a timing calibration. The secondary engine speed/timing sensor detects the reference for engine speed and timing from a timing ring on the camshaft timing gear. The timing ring consists of a notched pattern that has been machined onto a portion of the gear.The ECM counts the time between pulses that is created by the sensor as each gear rotates in order to determine rpm. Timing is provided by the unique pattern of notches in the timing ring.Under normal operation, the secondary engine speed/timing sensor is used to determine timing for starting purposes. The secondary engine speed/timing sensor is used to determine when the piston in the No. 1 cylinder is at the top of the compression stroke. When the timing has been established, the primary engine speed/timing sensor is then used to determine engine speed.When the timing has been established, the ECM triggers each injector in the correct firing order at the correct time. The actual timing and duration of each injection is based on engine rpm and on load. If the engine is running and the signal from one sensor is lost, no change in engine performance will be noticed. If the engine is running and the signals from both sensors are lost, fuel injection will be terminated. The engine is shut down by the ECM. The engine will start when only one sensor signal is present. The engine will not start