What is Caterpillar Fault Code CID1373?

Caterpillar CID1373 indicates a communication fault with Component Identification (CID) 1373, which typically refers to an aftertreatment or emissions system component, most commonly the Diesel Exhaust Fluid (DEF) Pump or Dosing Module. This code signals that the Electronic Control Module (ECM) cannot establish proper communication with this critical emissions control component via the CAN bus network.

This fault is particularly significant for modern Caterpillar excavators equipped with Tier 4 Final emissions systems. When CID1373 activates, the machine's aftertreatment system cannot properly inject DEF into the exhaust stream, compromising Selective Catalytic Reduction (SCR) performance. Left unresolved, this can trigger engine derate modes that severely limit machine productivity and potentially result in costly downtime on used equipment where component age is already a concern.

Common Symptoms

• Malfunction Indicator Lamp (MIL) or Check Engine Light illuminated on the instrument cluster
• Engine derate limiting machine power to 75% or lower after a programmed grace period
• DEF system warning messages displayed on the monitor screen
• Abnormal DEF consumption rates (either no consumption or excessive use)
• Regeneration failures or increased frequency of DPF regeneration cycles

Potential Causes

The most common technical causes for CID1373 on used Caterpillar excavators include:

• DEF pump internal failure due to crystallized urea contamination or worn internal components
• Damaged or corroded wiring harness between the ECM and DEF dosing module (particularly at connector pins)
• CAN bus communication issues caused by poor ground connections or resistance in network wiring
• Faulty DEF pump control module or internal circuit board corrosion from moisture intrusion
• Contaminated or degraded DEF fluid causing pump seizure or sensor malfunction
• ECM software version incompatibility after component replacement without proper calibration

How to Troubleshoot and Fix Code CID1373

Step 1: Perform Initial Diagnostic Scan Connect Caterpillar Electronic Technician (CAT ET) diagnostic software to retrieve active and logged fault codes. Document all related codes, particularly communication or aftertreatment system faults. Check the DEF tank level and fluid quality—contaminated or crystallized DEF is common in used machines.

Step 2: Inspect Wiring and Connections Physically inspect the DEF pump harness from the pump module to the ECM. On used excavators, check for harness chafing points near frame rails, hydraulic lines, and engine mounts. Clean all connector pins with electrical contact cleaner and inspect for corrosion, bent pins, or moisture intrusion. Use a multimeter to verify continuity through all harness circuits and check for proper ground resistance (should be less than 5 ohms).

Step 3: Test DEF Pump Communication With ignition on and engine off, use CAT ET to perform a DEF pump activation test. Listen for pump operation and measure supply voltage at the pump connector (should read 12V). If voltage is present but no communication occurs, measure CAN High and CAN Low signals (should read approximately 2.5V each with 120-ohm termination resistance across the pair).

Step 4: Component Replacement and Calibration If diagnostics confirm pump failure, replace the DEF dosing module assembly with genuine Caterpillar parts. After installation, perform ECM configuration using CAT ET to register the new component. Clear fault codes and complete a forced regeneration cycle to verify proper system operation.

Disclaimer: This guide provides general troubleshooting information. Always consult Caterpillar service manuals specific to your machine's serial number and seek qualified diesel technician assistance for complex repairs involving emissions systems and ECM programming.