350-62121-2 Tohatsu THRUST ROD

Illustration 1 g01304107
Engine speed signal
Use this procedure to troubleshoot suspect problems with the circuit for the engine speed sensor.This procedure covers the following diagnostic codes:
342-2 Secondary Engine Speed Sensor : Erratic, Intermittent, or Incorrect
342-5 Secondary Engine Speed Sensor : Current Below Normal
342-6 Secondary Engine Speed Sensor : Not Responding Properly
342-8 Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or PeriodRefer to Illustration 1. The engine speed sensor is powered by the sensor supply (12 VDC) from the Auxiliary Sensing Module (ASM). A magnetic pickup is located inside the sensor. As the teeth of the flywheel rotate past the magnetic pickup, the sensor generates a signal that indicates the rpm. The ASM monitors the signal from the engine speed sensor. The ASM uses the value of engine speed in order to perform calculations that relate to engine speed and load.The ASM sends a value that indicates engine speed to the master Electronic Control Module (ECM) via the Cat Data Link. The master ECM calculates a value that indicates engine rpm from the signal from the engine speed/timing sensor. The master ECM compares the two values.The master ECM activates a "342-2 Secondary Speed Sensor : Erratic, Intermittent, or Incorrect" diagnostic code and the master ECM shuts down the engine when all of the following conditions are true:
A "254-9 Electronic Control Module : Abnormal Update Rate" diagnostic code is not active. This indicates that the Cat Data Link is OK.
A "320-3" or "320-8" diagnostic code is not active. This indicates that the signal from the engine speed/timing sensor is OK.
The engine speed that is derived from the engine speed/timing sensor is greater than low idle.
The value of engine speed from the ASM and the engine speed that is derived from the engine speed/timing sensor are different by more than 50 rpm.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 sensor. The least likely cause is a problem with an ECM.Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print the logged codes to a file.The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.
Illustration 2 g01304145
Schematic for the circuit of the engine speed sensor
Test Step 1. INSPECT THE ELECTRICAL CONNECTORS AND WIRING
Remove the electrical power from the engine. Note: For the following steps, refer to Troubleshooting, "Electrical Connectors - Inspect".
Thoroughly inspect the following connections:
J5/P5 connectors
J9/P9 connectors
Check the torque of the allen head screw for the ECM connectors.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the engine speed sensor.
Illustration 3 g01304155
Rear view
(1) Engine speed sensor
Check the harness and wiring for abrasion and for pinch points from engine speed sensor (1) to each ECM. 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. MEASURE THE SENSOR SUPPLY VOLTAGE AT THE ENGINE SPEED SENSOR
Measure the supply voltage between terminals "A" and "B" at the harness connector for the sensor. Expected Result:The voltage is between 11.5 VDC and 13.5 VDC.Results:
OK - The sensor is receiving the correct supply voltage. Proceed to Test Step 3.
Not OK - The sensor is not receiving the correct supply voltage. There is a problem with the wiring for the sensor supply or the return.Repair: Make the necessary repairs to the harness and/or connectors.STOPTest Step 3. CHECK THE SIGNAL WIRE
Disconnect the harness connector for the engine speed sensor.
Use a jumper wire to connect terminals "B" and "C" at the harness connector for the sensor.
Disconnect the P5 connector.
Measure the resistance between terminals P5-41 and P5-51. Be sure to wiggle the wiring between the harness connector for the engine speed sensor and the P5 connector while you make the measurement. Expected Result:The resistance is less than five Ohms. The reading is stable while the wiring is wiggled.Results:
Yes - The resistance is less than five ohms. The reading is stable. Proceed to Test Step 4.
No - The resistance is greater than five ohms or the reading is unstable.Repair: Make the necessary repairs to the harness and/or connectors.STOPTest Step 4. CHECK THE INSTALLATION OF THE SENSORVerify that the engine speed sensor is installed correctly. Refer to the engine's Specification manual for the installation procedure.Expected Result:The sensor is installed incorrectly.Results:
OK - The sensor is installed correctly.Repair: Start the engine.If one of the following diagnostic codes is active, replace the engine speed sensor. Be sure to install the sensor correctly.
342-2 Secondary Engine Speed Sensor : Erratic, Intermittent, or Incorrect
342-5 Secondary Engine Speed Sensor : Current Below Normal
342-6 Secondary Engine Speed Sensor : Not Responding Properly
342-8 Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or PeriodSTOP
Not OK - The sensor is installed incorrectly.Repair: Perform the following procedure:
Install the sensor according to the procedure in the Specification manual.
Start the engine. If one of the following diagnostic codes is active, replace the engine speed sensor. Be sure to install the sensor correctly.
342-2 Secondary Engine Speed Sensor : Erratic, Intermittent, or Incorrect
342-5 Secondary Engine Speed Sensor : Current Below Normal
342-6 Secondary Engine Speed Sensor : Not Responding Properly
342-8 Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or PeriodSTOP