Komatsu PC70-8 Fault Code CA153: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code CA153?

Fault Code CA153 indicates a malfunction in the engine control system's communication circuit, specifically a CAN (Controller Area Network) communication error between the engine ECM (Engine Control Module) and other control units. This code triggers when the ECM detects abnormal or interrupted data transmission on the CAN bus network, which is the digital communication backbone connecting various electronic components on the PC70-8.

This fault is critical because the CAN network enables essential systems—including hydraulic controls, instrument cluster, and engine management—to exchange real-time data. When communication fails, the excavator may enter derate mode or experience reduced operational capability, directly impacting productivity and potentially causing secondary system errors.

Common Symptoms

• Warning lamp illuminated on the instrument panel (typically amber or red engine indicator)
• Reduced engine power or automatic derate to protect engine systems
• Erratic gauge readings or complete instrument cluster failure
• Hydraulic response delays or inconsistent operation due to lost coordination between systems
• Multiple fault codes appearing simultaneously as communication breakdown affects various modules

Potential Causes

The CA153 code on used PC70-8 excavators typically stems from:

• Damaged CAN bus wiring harness, particularly at known rub points near the swing motor, boom base, or along the chassis rail where harnesses flex during operation
• Corroded or loose connector terminals at the ECM (located under the operator's cab) or junction boxes exposed to moisture ingress
• Failed termination resistors within the CAN network (120-ohm resistors at network endpoints)
• ECM internal communication module failure due to age-related component degradation
• Voltage fluctuations from weak batteries or failing alternators affecting CAN bus stability (CAN requires stable 9-16V operation)

How to Troubleshoot and Fix Code CA153

Step 1: Visual Inspection Thoroughly inspect the main wiring harness from the ECM to all connection points. On used machines, focus on areas where harnesses contact metal edges or moving components. Check all connector pins for corrosion, bent terminals, or moisture. Clean with electrical contact cleaner if necessary.

Step 2: Voltage and Resistance Testing Using a digital multimeter, verify battery voltage is stable (12-14V). Check CAN bus termination resistance between CAN-H and CAN-L wires at the ECM connector—should read approximately 60 ohms (two 120-ohm resistors in parallel). Test for shorts to ground on both CAN lines (should show infinite resistance).

Step 3: CAN Signal Verification Connect Komatsu diagnostic software (KOMTRAX or equivalent) to monitor live CAN communication. Observe for intermittent dropouts or error frames. Wiggle harnesses while monitoring to identify loose connections.

Step 4: Component Replacement If wiring and connections test normal, replace the ECM or suspected faulty control module. For used excavators, always verify compatibility of replacement ECMs with your machine's production year and software version.

Disclaimer: This guide provides general troubleshooting steps. Complex electrical diagnostics should be performed by certified Komatsu technicians with proper diagnostic equipment. Incorrect repairs may cause additional system damage.