SEAL 8P1251 - Caterpillar

Illustration 1 g01757581
Blade Raise (Y-Axis-Raise/Lower) position sensor schematicA CID 1078 diagnostic code is associated with the Blade Raise (Y-Axis-Raise/Lower) position sensor for the blade up and down commands. An FMI 03 indicates the machine ECM has found the voltage in the sensor circuit above normal.Possible causes for this diagnostic code are:
Failed sensor power supply.
Failed sensor.
Open sensor circuit wire.
Shorted sensor signal output wire.
Failed machine ECM. This condition is unlikely.Note: Poor connections often cause problems in electrical circuits. Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all circuit connections are clean, secure, and in good condition. If a problem is found with any of the connections: correct the problem, and verify that diagnostic code CID 1078 FMI 03 is still active, before performing the following procedures.System Response:This diagnostic code will disable the Blade up and down functions.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes now, but clear those codes after the original diagnostic code has been corrected.Test Step 1. VERIFY THE +10 VDC POWER SUPPLY
Turn the disconnect switch and the key start switch to the "ON" position.
Do not disconnect any of the machine harness connectors at this time.
At the connector for the Blade Raise (Y-Axis-Raise/Lower) position sensor, measure voltage between contact 1 (wire A709-OR) and contact 2 (wire J765-BU) in the sensor connector.Expected Result:The voltage is 10.0 0.5 VDC.Results:
YES - The voltage is 10.0 0.5 VDC. Go to Test Step 2.
NO - The voltage is not 10.0 0.5 VDC. There is a problem with the ECM +10 VDC power supply.Repair: Refer to the complete electrical schematics for the machine. Investigate and repair the ECM +10 VDC power supply problem. After the ECM +10 VDC power supply problem is repaired, check if the CID 1078 FMI 03 diagnostic code is still active. If the diagnostic code is still active, proceed to Test Step 2. If the diagnostic code is no longer active, and does not exist at this time, return the machine to normal operation.Test Step 2. CHECK THE SENSOR, THE ECM, AND THE MACHINE HARNESS
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the harness connector from the Blade Raise (Y-Axis-Raise/Lower) position sensor.
In the sensor harness connector, place a jumper wire between the contact for wire H710-PK, and the contact for wire J765-BU in the connector.
Turn the key start switch and the disconnect switch to the ON position.
Observe the status of the diagnostic code.Expected Result:The 1078 FMI 03 diagnostic code remains active.Results:
YES - The diagnostic code remains active. The sensor is not the problem. Go to Test Step 3.
NO - The diagnostic code is no longer active, and has been replaced by an active CID 1078 FMI 04 diagnostic code. The sensor has failed. Repair: Replace the sensor. Go to Test Step 5.Test Step 3. CHECK THE SENSOR CIRCUIT FOR AN OPEN WIRE
Turn the disconnect switch and the key start switch to the OFF position.
The sensor remain disconnected from