CORK 2B7559 - Caterpillar

Illustration 1 g03345445
Schematic for the Brake Pump pressure sensor
This diagnostic code is associated with the Brake Pump pressure sensor. An FMI 20 means the Brake ECM has determined the data has drifted high, the sensor signal output is above normal.The sensor outputs a Pulse Width Modulated (PWM) active analog signal to inform the Brake ECM of the hydraulic pressure in the Brake Pump. Possible causes of this diagnostic code are:
The ECM believes that the Service Brake Accumulator Pressure sensor has failed in range.
There is a problem with the physical sensor.
The sensor has failed.
There is a problem with the hydraulic system whereby the brake accumulators are not draining properly.
The Service Brake Accumulator sensor reports a difference in pressure exceeding 2345 kPa (340 psi), after the Brake Accumulators have purged completely, and the engine is not running.
The Brake ECM may have failed, but is unlikely.Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all the machine harnesses and connectors involved in the circuit. Make sure to verify that all of the connections in the circuit are clean, secure, and in good condition. Correct any problems found with any of the connections. Verify the diagnostic code CID 1962 FMI 20 is still active, before continuing with this procedure.Note: The following test procedure may create other diagnostic codes. Ignore all the created diagnostic codes now, but clear all those codes after the cause for the original diagnostic code has been corrected.Test Step 1. CHECK IF THE DIAGNOSTIC CODE REMAINS.
There is a problem with the physical sensor. Expected Result:The physical sensor is fine.Results:
YES - The physical sensor is fine. Proceed to step 2.
NO - The physical sensor is not fine.Repair: Repair or replace the physical sensor.See Testing and Adjusting, KENR8738, "793F BRAKING SYSTEM" or Testing and Adjusting, KENR8374, "797F BRAKING SYSTEM".STOPTest Step 2.
There is a problem with the hydraulic system whereby the Brake accumulators are not draining properly. Expected Result:The hydraulic system whereby the Brake accumulators are draining properly.Results:
YES - The hydraulic system whereby the Brake accumulators are draining properly. Proceed to step 3.
NO - The hydraulic system whereby the Brake accumulators are not draining properly.Repair: Troubleshoot the hydraulic system and the Brake accumulators. Repair or replace the faulty parts.See Testing and Adjusting, KENR8738, "793F BRAKING SYSTEM" or Testing and Adjusting, KENR8374, "797F BRAKING SYSTEM".STOPTest Step 3.
Inspect the contacts of the harness connectors and clean the connectors. Check the wires for damage to the insulation that is caused by excessive heat, corrosion, or chafing.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit.
Turn the disconnect switch and the key start switch to the ON position.
Clear all inactive diagnostic codes.
Operate the machine.
Check the status of the CID 1962 FMI 20 code. Expected Result:The CID 1962 FMI 20 diagnostic code is active.Results:
YES - The CID 1962 FMI 20 The CID 1961 FMI 20 diagnostic code is active. Repair: Failure of the Brake ECM is unlikely. Exit this