SPRING-LIFTER 4P8704 - Caterpillar

Illustration 1 g02065914
Schematic for the Boom Up Pilot Pressure sensor
This diagnostic code is associated with the Boom Up Pilot Pressure sensor. An FMI 04 diagnostic code means the machine ECM has determined the voltage in the sensor signal output circuit is below normal. Possible causes of this diagnostic code are:
The sensor may have failed.
The sensor output signal may be shorted to ground.
The Machine ECM may have failed. A failure of the Machine ECM is unlikely.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. Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all of the connections in the circuit 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 2429 FMI 04 is still active, before performing the following procedures. Test Step 1. CHECK THE SENSOR, THE ECM, AND THE CIRCUIT CONNECTIONS IN THE MACHINE HARNESS.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connector from the Boom Up Pilot Pressure sensor.
Turn the key start switch and the disconnect switch to the ON position. Do NOT start the engine.
Observe the status of the diagnostic code. Expected Result:The CID 2429 FMI 04 diagnostic code does not change. Results:
YES - The diagnostic code does not change, and remains active. The sensor is NOT the cause of the problem. The machine harness may have failed, or the ECM may have failed. Go to Test Step 2.
NO - The CID 2429 FMI 04 diagnostic code is no longer active, and has changed into an active CID 2429 FMI 03 diagnostic code. The ECM has detected this valid diagnostic code. The ECM, and the harness, are correct. The sensor has failed. Replace the sensor. Go to Test Step 3. Test Step 2. CHECK THE SENSOR OUTPUT SIGNAL FOR A SHORT TO GROUND.
Turn the disconnect switch and the key start switch to the OFF position.
At the machine ECM, disconnect the J1 and J2 machine harness connectors from the ECM.
The harness connector remains disconnected from the Boom Up Pilot Pressure sensor.
At the ECM J1 harness connector, measure the resistance between the pin for contact J1-16 (M843-PU(Purple)) and all of the other contacts used in the ECM harness connectors. Expected Result:Each measurement is more than 5000 ohms.Results:
YES - Each measurement is more than 5000 ohms. The sensor output signal circuit is NOT shorted to ground. Go to Test Step 3.
NO - One or more of the measurements are NOT more than 5000 ohms. There is a short in the harness. The short is between the sensor output signal wire and the wire with the low resistance. Repair, or replace, the harness. Go to Test Step 3. Test Step 3. CHECK IF THE DIAGNOSTIC CODE IS