SHIM 1772482 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine speed/timing sensor or if a diagnostic code in Table 1 is active.
Table 1
Diagnostic Codes Table    
Code and Description    Conditions which Generate this Code    System Response    
190-8 Engine Speed Sensor abnormal frequency, pulse width, or period     The engine speed is greater than zero rpm and the pattern from the timing ring is incorrect for five seconds.     The engine speed is set to zero rpm.
The code is active.
The code is logged if the pattern from the timing ring returns for five seconds.    
342-8 Secondary Engine Speed Sensor abnormal frequency, pulse width, or period    The Electronic Control Module (ECM) provides the engine speed/timing sensor with 12 1 VDC. The engine speed/timing sensor provides a pulse signal to the ECM. The signal is created as the timing reference gear rotates past the pickup of the engine speed/timing sensors. The timing reference gear is mounted on the rear of the left camshaft. A unique tooth pattern on the timing reference gear allows the ECM to determine the crankshaft position, rotation, and rpm.If the primary engine speed/timing sensor fails, the ECM will use the secondary engine speed/timing sensor until electrical power is removed from the ECM. In order to prevent any unnecessary down time, the primary engine speed/timing sensor should be repaired or replaced at the earliest possible convenience.The engine speed/timing sensor generates a pulse signal to the ECM as each tooth of the timing reference gear passes the sensor. The ECM counts the pulses in order to determine the engine rpm. The ECM memorizes the pattern of the pulses. The ECM compares that pattern to a standard pattern in order to determine the crankshaft position. The ECM uses this information to determine the position of the No. 1 piston. The ECM then triggers each fuel injector to fire in the correct firing order and at the correct time. The actual timing and duration of each injection is determined by the ECM. The ECM uses engine rpm and engine load to determine the timing and duration of injection. The loss of the signal from the engine speed/timing sensor generates a diagnostic code. The loss of the signals from both of the engine speed/timing sensors triggers the termination of the signals to the fuel injectors.
Illustration 1 g01265854
Schematic for the engine speed/timing sensors and the timing calibration sensorTest Step 1. Inspect Electrical Connectors and Wiring
Turn the switch that provides power to the keyswitch input for the ECM to the OFF position.
Turn the breaker for the ECM to the OFF position.
Illustration 2 g01228838
Location of the J1/P1 ECM connectors (typical front side engine view) (1) J1/P1 ECM connectors
Illustration 3 g01215178
Location of the engine speed/timing sensors (typical left side engine view) (2) Primary engine speed/timing sensor (3) Secondary engine speed/timing sensor
Illustration 4 g01228794
Location of the timing calibration probe (typical right side engine view) (4) Timing calibration sensor
Thoroughly inspect connectors (1). Also, thoroughly inspect the connectors