What is Caterpillar Fault Code CID587?

Caterpillar fault code CID587 indicates a problem with the DEF (Diesel Exhaust Fluid) pump motor circuit, specifically detecting an abnormal current or voltage condition in the pump control system. This Component ID (CID) is part of Caterpillar's electronic diagnostic system that monitors the aftertreatment components required for emissions compliance. The DEF pump is responsible for injecting precise amounts of diesel exhaust fluid into the exhaust stream to reduce NOx emissions through the Selective Catalytic Reduction (SCR) system.

This fault is critical because a malfunctioning DEF pump can cause the machine to enter derate mode, significantly reducing engine power and potentially bringing operations to a halt. On used excavators, this code often appears due to accumulated wear on electrical components or fluid contamination affecting pump operation.

Common Symptoms

• Check Engine Light or Malfunction Indicator Lamp (MIL) illuminated on the instrument panel
• Engine derate or reduced power output, particularly noticeable during heavy digging operations
• DEF system warning messages displayed on the monitor screen
• Audible alarm or continuous beeping when the machine is operating
• Potential inability to regenerate the diesel particulate filter (DPF) properly

Potential Causes

The most common technical causes for CID587 on used Caterpillar excavators include:

• DEF pump motor failure due to internal wear, contaminated DEF fluid, or crystallization buildup
• Wiring harness damage at known rub points near the pump mounting location or along the chassis rail
• Corroded or loose electrical connectors at the pump harness connection (common in machines exposed to harsh environments)
• ECM (Engine Control Module) internal fault in the pump driver circuit
• Low voltage supply to the pump caused by battery issues or poor ground connections
• Contaminated DEF fluid causing pump mechanical seizure or increased current draw

How to Troubleshoot and Fix Code CID587

Step 1: Visual Inspection Begin by inspecting the DEF pump and its wiring harness for obvious damage. On used excavators, check for harness chafing where wires route near frame members or moving components. Inspect all connectors for corrosion, bent pins, or moisture intrusion—clean with electrical contact cleaner if necessary.

Step 2: Electrical Testing Using Caterpillar Electronic Technician (Cat ET) diagnostic software, monitor the DEF pump current draw during operation. Normal operating current typically ranges from 3-8 amps. Use a digital multimeter to verify voltage supply at the pump connector (should be battery voltage when commanded on). Check ground circuit resistance—it should be less than 1 ohm.

Step 3: Component Testing Disconnect the DEF pump harness and measure resistance across the motor terminals (typically 2-4 ohms for a healthy pump). If resistance is infinite (open circuit) or near zero (short circuit), the pump motor has failed. Before replacing the pump on used machines, drain and inspect the DEF tank for contamination or crystallization that may have damaged the pump.

Step 4: Verification After repairs, clear the fault code using Cat ET, perform a pump function test, and run the machine through a complete operating cycle to ensure the code doesn't return.

Disclaimer: This guide provides general troubleshooting information. Always consult the manufacturer's service manual and consider professional diagnostic assistance for complex electrical issues or if you lack proper diagnostic tools.