GEAR-SUN 7Y1491 - Caterpillar

Illustration 1 g03371948
Schematic of the Lift Linkage (Self Level) Limit Switch
This diagnostic code is recorded when the ECM records an erratic signal or an intermittent signal from the Lift linkage limit switch. There could be a short to the +battery circuit, a short to ground, or an open circuit. The ECM could also be receiving invalid combinations from the switch. The switch connects to contact J1-74 (wire T867-BU(Blue)) and contact J2-60 (wire T868-YL(Yellow)).The "Lift Linkage Limit Switch" is the position switch for the self level feature. The switch is located near the right-hand side lift arm, near where the lift arm linkage pin is located.The possible causes for this diagnostic code are listed:
The signal circuit is open.
The +battery circuit from the electrical system to the switch is open.
The signal circuit is shorted to the +battery circuit.
The signal circuit is shorted to ground.System Response:The implements will stop working until the right-hand joystick is returned to the center position. After the joystick has been centered, the implements will behave normally, but the following features will be disabled:
Self Level
Return-to-Dig
Lift Snubbing
Work Tool PositionerThe green Self Level icon on the machine left-hand display will no longer light up when the Self Level Cab switch is turned on. In the case of an intermittent fault, these features will be disabled until the next key cycle.Note: Ensure that CID 3915 FMI 04 is active.Test Step 1. Check The ECM And The Harness
Turn the disconnect switch and the key start switch to the ON position.
Disconnect the harness from the sensor.
At the harness connector for the sensor, measure the voltage between contact 1 (wire P769-YL(Yellow)) and contact 4 (wire P770-WH(White)). Expected Result:The voltage measures approximately 8 1.0 VDC.Results:
YES - The voltage measures approximately 8 1.0 VDC. Proceed to test step 2.
NO - The voltage does NOT measure battery voltage. The ECM has failed or the harness has failed. Proceed to test step 5.Test Step 2. Check The ECM And The Harness
The harness remains disconnected from the sensor.
At the harness connector for the switch, measure the voltage between contacts 2 (wire T867-BU(Blue)) and ground contact 4 (wire P770-WH(White)). Expected Result:The voltage measures approximately 8 1.0 VDC.Results:
YES - The voltage measures approximately 8 1.0 VDC. The harness is correct.Repair: Replace the switch.STOP
NO - The voltage is above 8.0 1.0 VDC. The ECM has failed or the harness has failed. Proceed to test step 3.
NO - The voltage is below 8 1.0 VDC. The ECM has failed or the harness has failed. Proceed to test step 4.Test Step 3. Check For A Shorted Harness
The sensor remains disconnected.
Turn the disconnect switch and the key start switch to the OFF position.
Disconnect the harness connectors (J1 and J2) from the ECM.
At the harness connectors for the ECM (J1 and J2), measure the resistance between contact J1-74 (wire T867-BU(Blue)) and ALL other J1 and J2 connector contacts. Expected Result:The resistance is greater than 5000 Ohms.Results:
YES - The resistance is greater than 5000 Ohms. The harness resistance is correct.Repair: ECM