STOP COLLAR 4C6598 - Caterpillar

Engine Oil Pressure Signal Check
The engine oil pressure signal circuit connects to Socket 5 of connector Receptacle B (Wire 405-GY). The engine oil pressure signal is either HIGH or LOW. The conditions for the HIGH or LOW signal are:* LOW signal (less than 1 DCV). Engine stopped (NO oil pressure).* HIGH signal (greater than 5 DCV). Engine running (oil pressure present).The source of the engine oil pressure signal for the engine overspeed alarm is a 9X-4276 Pressure Switch. The engine oil pressure signal also connects to the low engine oil pressure indicator dash lamp. If the signal is failed, a problem with the operation of the EMS also exists.Engine Oil Pressure Switch Check
The engine oil pressure switch (Terminals 1 & 3) functions as follows:* Switch is closed (or low) with the engine stopped.* Switch is open (or high) with the engine running.If faulty operation of the engine oil pressure switch is suspected, perform the following check. The engine oil pressure switch (Terminals 1 & 3) also connects to the low engine oil pressure indicator dash lamp. If the switch is failed, a problem with the operation of the low engine oil pressure indicator dash lamp also exists. Terminals 1 and 2 run the service hour meter. Procedure1. Stop the engine. Disconnect the wires from the engine oil pressure switch. Check for continuity across the normally closed switch terminals. (Terminals 1 and 3 on the switch.) Allow enough time for the oil pressure to bleed down after stopping the engine. The correct result is continuity.* There is NO continuity; the switch is failed. Replace the engine oil pressure switch.* There is continuity; go to 2.2. Start the engine. Check for continuity across Terminals 1 and 3 on the switch. The correct result is NO continuity.* There is NO continuity; the switch is good.* There is continuity; the switch is failed. Replace the engine oil pressure switch. For a more precise test, bench test the engine oil pressure switch.The engine oil pressure switch specifications are: Actuation pressure ... 93.0 20.8 kPa (14.0 3.0 psi)Deactuation pressure ... 68.9 20.8 kPa (10.0 3.0 psi)Switch Terminals 1 and 3 normally closed below ... 68.9 20.8 kPa (10.0 3.0 psi)System Test
Illustration 18. Engine Overspeed Alarm Control
(1) Diagnostic Lamp #1. (2) Diagnostic Lamp #2. (3) Diagnostic Lamp #3. (4) Diagnostic Lamp #4. (5) Connector Plug A. (6) Connector Receptacle B. The warning indicators and the engine speed pickup must function correctly before performing this test. See Warning Indicator Test and Problem 2, Engine Speed Signal.This test determines if the engine overspeed control is operating correctly. Perform the test only if there is an unexplained system failure. Installation of the system test harness places the engine overspeed control in the system test mode. This decreases (to a normal operating range) the defined RPM values at which the warning indicators are activated. Correct operation of the engine overspeed control is verified by increasing and decreasing the RPM in