PISTON G BASIC 4N0502 - Caterpillar

Illustration 1 g02026254
Boom"Overload Pressure" sensor circuit schematic
This diagnostic code is for the Boom"Overload Pressure" sensor. An FMI 08 diagnostic code means the machine ECM has determined the sensor output signal has an abnormal frequency, pulse width, or period. Possible causes for this diagnostic code are:
Failed sensor.
Short circuit to the sensor output signal wire.
Failed machine ECM, but most 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 1178 FMI 08 is still active, before performing the following procedures. System Response:This failure may result in erratic movement of the machine. Test Step 1. CHECK THE SENSOR, THE ECM, AND THE MACHINE HARNESS.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connector from the Boom"Overload Pressure" sensor.
In the harness connector for the sensor, place a jumper wire between the contact for terminal C (wire H446-PK(Pink)) and the contact for terminal B (wire A209-BK(Black)) in the sensor connector.
Turn the key start switch and the disconnect switch to the ON position.
Observe the status of the diagnostic code. Expected Result:The 1178 FMI 08 diagnostic code remains active. Results:
YES - The CID 1178 FMI 08 diagnostic code remains active. The sensor is not causing the problem. Go to Test Step 2.
NO - The CID 1178 FMI 08 diagnostic code is no longer active. The diagnostic code has been replaced by an active CID 1178 with a different FMI code. The sensor has failed. Repair: Replace the sensor. Go to Test Step 3.Test Step 2. CHECK THE MACHINE HARNESS FOR A SHORT CIRCUIT.
Turn the key start switch and the disconnect switch to the OFF position.
The sensor remains disconnected from the harness connector.
Remove the jumper wire from the connector.
Disconnect both the J1 and J2 harness connector from the machine ECM.
At the ECM J1 harness connector , measure the resistance between contact J1-37 (wire H446-PK(Pink)) and frame ground.
Again at the ECM J1 harness connector , measure the resistance between contact J1-37 (wire H446-PK(Pink)) and all of the other contacts that are used in both the J1 and J1 ECM harness connectors. Expected Result:All resistance readings are greater than 5000 ohms. Results:
YES - All resistance readings are greater than 5000 ohms. Go to Test Step 3.
NO - All resistance readings are not greater than 5000 ohms. There is a short circuit in the machine harness. Repair: Repair or replace the harness.Go to Test Step 3.Test Step 3. CHECK THE DIAGNOSTIC CODE STATUS.
Reconnect all disconnected machine harness connectors. Make sure that all the connectors are fully seated. Observe that the clips for