921503-0315 Tohatsu SCREW

Illustration 1 g01272867
Schematic for the tachometer circuit
Illustration 2 g01272878
Schematic for the tachometer circuit
Test Step 1. Inspect the Electrical Connectors and the Wiring
Illustration 3 g01152498
Terminal locations on the P1 connector
(P1-38) Tachometer+
(P1-39) Tachometer-
Thoroughly inspect ECM connector J1/P1 and the terminals for the tachometer. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Refer to Illustration 3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the terminals for the tachometer:
Check the allen head screw on each of the ECM connectors for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Check the harness and wiring for abrasion and for pinch points from the tachometer to the ECM. Expected Result:All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
Yes - The wiring is OK. Proceed to Test Step 2.
Not OK - The wiring is not OK. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Check the ECM Connection to the TachometerNote: Some tachometers require only one signal line in order to operate. Either of the ECM terminals can be used for this type of tachometer. The other terminal is open. If both wires are connected, and one indicates an open circuit, repair this open wire.Verify that the connections for the tachometer are correct at the P1 connector.Expected Result:The P1 connections are correct.Results:
OK - The P1 connections are OK. Proceed to Test Step 3.
Not OK - The P1 connections are Not OK.Repair: Repair the connections or replace the connectors.STOPTest Step 3. Use Caterpillar Electronic Technician (ET) to Check the Tachometer Signal
Establish communication between Cat ET and the ECM.
Access the tachometer special test. Access the following display screens in order:
"Diagnostics"
"Diagnostic Tests"
"Special Test"
While the dash tachometer is being monitored, begin the test. Expected Result:RESULT 1 The dash tachometer indicates approximately 1500 150 rpm and the dash tachometer is stable.RESULT 2 The tachometer does not indicate an engine rpm or the tachometer is erratic.RESULT 3 The tachometer rpm is stable but the tachometer rpm is not within 50 rpm of 1500 rpm.Results:
Result 1 - The ECM and the tachometer are OK.Repair: There may be an intermittent problem in the harness and/or in the connectors. Repair the harness and the connectors. Verify that the original problem has been resolved.STOP
Result 2 - The engine rpm is not indicated or the engine rpm is erratic. Proceed to Test Step 4.
Result 3 - The engine rpm is not within 50 rpm of 1500 rpm. Proceed to Test Step 5.Test Step 4. Check the Tachometer Signal
Illustration 4 g01152502
ECM breakout T-connector
(38) Tachometer+
(39) Tachometer- Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of measuring a PWM duty cycle.
Disconnect the P1 connector.
Connect a breakout T to the ECM connector P1.
Fabricate two jumper wires 100 mm (4 inch) long. Crimp a Deutsch Pin to one end of each wire.
Refer to Illustration 4. Insert one of the jumper wires into terminal P1-39 of the breakout T and insert the other jumper wire into terminal P1-38 of the breakout T.
Access the tachometer special test. Access the following display screens in order:
"Diagnostics"
"Diagnostic Tests"
"Special Test"
Attach one of the multimeter leads to the jumper wire from P1-38.
Attach the other multimeter lead to the jumper wire from P1-39.
While the tachometer special test is being run, observe the reading on the multimeter. Expected Result:The multimeter indicates a duty cycle from 30 to 70 percent from each of the terminals for the tachometer while the engine is running.Results:
OK - The multimeter indicates a duty cycle from 30 to 70 percent. The ECM tachometer output is OK. Return the wiring to the original configuration. Proceed to Test Step 6.
Not OK - The duty cycle is not within the specification.Repair: Perform the following repair:
Restore the wiring to the original configuration.
Temporarily connect a test ECM.
Check the system for active diagnostic codes.
If the problem is resolved with the test ECM, connect the original ECM. Test the tachometer again.
If the problem returns with the original ECM, replace the ECM.
Verify that the repair eliminates the problem. STOPTest Step 5. Check the Tachometer Calibration
Determine the tachometer engine speed calibration setting in pulses per revolution.
Verify that the value of the "Tachometer Calibration" parameter matches the requirements of the tachometer. Expected Result:The parameter is programmed correctly.Results:
OK - The parameter is programmed correctly.Repair: Replace the tachometer. Verify that the repair eliminates the problem.STOP
Not OK - The parameter is not programmed correctly.Repair: Program the parameter with the correct value. Verify that the repair eliminates the problem.STOPTest Step 6. Check the ECM Connection to the Tachometer
Refer to Illustration 4. Remove the appropriate terminal