BUSHING 1137794 - 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 one of the diagnostic codes in Table 1 is active.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
190-2 Engine Speed Sensor erratic, intermittent, or incorrect The engine speed signal cannot be detected. The timing gear pattern returns within one second before being lost and the battery voltage is greater than 9 VDC for the last two seconds. The code will be active and logged if the Electronic Control Module (ECM) detects an incorrect signal for one second. The battery voltage is greater than 9 VDC for the last two seconds. The engine speed is set to zero rpm.
The code is logged only if the engine has been running for three seconds.
190-3 Engine Speed Sensor voltage above normal A wire on the engine speed/timing sensor is disconnected and/or broken. There is a short circuit to the +Battery terminal. The engine speed is set to zero rpm.
The code is logged.
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. The ECM provides the engine speed/timing sensor with 12.5 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 sensor. 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.The engine speed/timing sensor generates a pulse signal to the ECM as each tooth 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 cylinder. The ECM then triggers each unit 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 an alert on the Caterpillar Electronic Technician (ET). The loss of the signal from the engine speed/timing sensor triggers the termination of the signals to the fuel injectors by the ECM.Note: If the engine timing gear is installed backward, the diagnostic code 190-08 will be generated. If this code is active, the ECM will not fire the injectors.
Illustration 1 g01241934
Typical schematic
Illustration 2 g01216172
P1 ECM connector
(P1-5) Digital return
(P1-33) Engine speed/timing signal
(P1-40) Engine timing calibration -
(P1-41) Engine