CAMSHAFT AS 1007408 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the engine speed/timing sensor or if the diagnostic code in Table 1 is active.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
190-8 Engine Speed signal abnormal The engine speed is greater than zero rpm and the pattern from the timing ring is incorrect for 5 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 5 seconds. The Electronic Control Module (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 g03338089
Typical schematic
Illustration 2 g03338092
P1 ECM connector
(P1-33) Engine speed/timing signal
(P1-40) Engine timing calibration -
(P1-41) Engine timing calibration +
(P1-43) +12.5 V supply
(P1-51) Digital return
Illustration 3 g01218411
Left side view
(1) Engine speed/timing sensor
Illustration 4 g01234146
Location of ECM connectors
Test Step 1. Inspect Electrical Connectors and Wiring
Remove electrical power from the ECM.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors for the circuit. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All connectors, pins, and sockets are coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion or of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK -