SENSOR GP-SPEED 7R3145 - Caterpillar

System Operation Description:
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Typical example of a speed/timing sensor and timing ringThe speed/timing sensor provides information about engine speed and the position of the crankshaft to the control module for the Electronic Ignition System (EIS). The sensor is powered by a sensor supply (13 VDC) from the control module. The sensor is a magnetic pickup. The timing ring is mounted on the rear of the left camshaft. As the teeth of the ring rotate past the sensor, the sensor generates a signal that matches the pattern of the teeth.The timing ring has a special tooth pattern that indicates the position of the camshaft and the direction of rotation. When the engine rotates in the normal direction, the slots pass the speed/timing sensor in a particular order.With the information from the engine speed/timing sensor, the EIS control module is able to calculate the positions of the pistons in the cylinders. The control module determines the desired ignition timing according to the engine speed and load. If detonation is detected, the control module retards the timing of the affected bank of cylinders. The control module sends voltage pulses to the ignition transformers for firing the spark plugs according to the desired timing.During engine operation, the control module will shut down the engine if the module detects a problem with the signal from the speed/timing sensor. The control module will also generate a diagnostic code.If there is a problem with the sensor signal during start-up but no diagnostic code is generated, the control module will not initiate the ignition. The engine will not start. The corresponding diagnostic code is not generated.The most likely causes of the diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with the engine speed/timing sensor. The least likely cause is a problem with the EIS control module.
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Schematic diagram for the speed/timing sensor
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Schematic diagram for the speed/timing sensorThe engine is configured for Canadian Standards Association (CSA).Test Step 1. Inspect the Electrical Connectors and Wiring.
Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
Thoroughly inspect the following connections:
EIS connector
Connectors for the speed/timing sensor
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Speed/timing sensor
Check the harness and wiring for abrasion and for pinch points from the speed/timing sensor to the control module.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the speed/timing sensor.Expected Result:The connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - The components are in good condition with proper connections. Proceed to Test Step 2.
Not OK - The components are not in good condition and/or at least one connection is improper.Repair: Perform the necessary repairs and/or replace parts, if necessary.STOPTest Step 2. Check for a Diagnostic Code
Restore the electrical power to the engine.
Connect an electronic service tool to a service tool connector.
Clear any