COVER AS 3W1900 - Caterpillar

Test Step 1. Use Caterpillar Electronic Technician (ET) to Check the ECM Tachometer Signal
Connect the Cat ET at the data link connector.
Turn the keyswitch to the ON position.
Access the "Tachometer Circuit 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 does not indicate an engine speed that is within 50 rpm of 1500 rpm.Results:
Result 1 - The ECM and the tachometer are OK.STOP
Result 2 - The engine rpm is not indicated or the engine rpm is erratic. Proceed to Test Step 2.
Result 3 - The engine rpm is not within 50 rpm of 1500 rpm. Proceed to Test Step 6.Test Step 2. Determine the Type of Connection for the Tachometer Circuit
Determine if the wiring for the tachometer is wired directly to the ECM or through the J1939 or J1587 data link.Expected Result:The tachometer is wired directly to the ECM.Results:
OK - The tachometer is wired directly to the ECM. Proceed to Test Step 3.
J1939 data link - The tachometer is wired through the J1939 data link.Repair: Refer to Troubleshooting, "Powertrain Data Link Circuit - Test".STOP
J1587 data link - The tachometer is wired through the J1587 data link.Repair: Refer to Troubleshooting, "ATA (SAE J1587 / J1708) Data Link Circuit - Test".STOPTest Step 3. Inspect the Electrical Connectors and the Wiring
Thoroughly inspect the J1/P1 ECM connector, the firewall bulkhead connector, and the terminals for the tachometer in the connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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:
P1-11
P1-17
Check the allen head screws for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasion and for pinch points from the battery 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 or of pinch points.Results:
OK - Proceed to Test Step 4.
Not OK - Repair: Perform the following 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 4. Check the ECM Connection to the Tachometer
Inspect the J1/P1 ECM connector. Verify that the connections are present at P1-11 (tachometer-) and at P1-17 (tachometer+).Note: Some of the tachometers require only one signal line to be connected. Either of the ECM terminals can be used for this type of tachometer. The other wire should be left disconnected. If both wires are connected, and one indicates an open circuit, repair this line.Expected Result:Wires are