What is Doosan Excavator Fault Code E000157-21?

Fault Code E000157-21 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically a CAN bus communication error between the engine controller and the main machine controller. This diagnostic trouble code (DTC) is triggered when the ECM detects an interruption, voltage irregularity, or complete loss of data transmission on the Controller Area Network (CAN) system.

In Doosan excavators, the CAN bus serves as the critical communication highway between multiple electronic control units. When E000157-21 appears, the engine ECM cannot properly exchange operational data with the machine's main controller, affecting coordinated functions like engine speed requests, hydraulic system demands, and monitoring systems. This fault is particularly critical because it can cause the machine to enter limp mode or prevent startup entirely, directly impacting productivity on job sites.

Common Symptoms

When fault code E000157-21 is active, operators typically experience:

• Engine warning light illuminated on the instrument panel, often accompanied by a check engine indicator
• Intermittent or complete loss of communication between display monitor and engine, showing blank readings or frozen data
• Machine entering derate mode with reduced engine power or RPM limitations
• Erratic hydraulic performance due to improper coordination between engine output and hydraulic demands
• Difficulty starting the machine, or engine starting then immediately shutting down due to communication failure

Potential Causes

The most common technical reasons for E000157-21 in used Doosan excavators include:

• Damaged or corroded CAN bus wiring harness, particularly at flex points near the engine mount or cab pivot where repeated movement causes wire chafing
• Loose or corroded connector terminals on ECM or main controller connectors, especially in machines exposed to moisture or harsh environments
• Failed termination resistors in the CAN network causing signal reflection and communication errors
• ECM or main controller internal failure, though less common than wiring issues
• Voltage supply problems to either control module due to failing relays, poor grounds, or battery issues
• Aftermarket accessory installations that improperly tap into the CAN network

How to Troubleshoot and Fix Code E000157-21

Step 1: Visual Inspection Begin with a thorough physical inspection of all wiring harnesses between the engine ECM and main controller. On used excavators, focus on known wear points: cable routing near the engine mounting brackets, harness passages through bulkheads, and areas where cables contact frame members. Look for abraded insulation, pinched wires, or evidence of rodent damage. Inspect all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, check for proper CAN bus voltage at both ECM and main controller connectors. With ignition on and engine off, you should measure approximately 2.5V on CAN High and CAN Low lines (with some variation depending on network state). Measure termination resistance between CAN High and CAN Low—you should read approximately 60 ohms with all modules connected, indicating proper 120-ohm resistors at each network end. Any reading significantly different suggests open circuits, shorts, or missing termination.

Step 3: Advanced Diagnostics Connect Doosan diagnostic software (G-SCAN or equivalent dealer-level tool) to monitor live CAN bus communication. Check for intermittent dropouts or error frames. Test power supply circuits to both controllers—verify battery voltage reaches ECM and main controller with less than 0.5V drop. Check all ground connections, as poor grounds are frequent culprits in used machines. Clean ground points to bare metal and apply dielectric grease.

Step 4: Component Replacement If wiring and connections test properly, suspect ECM or controller failure. Before replacing expensive modules in used equipment, consider having the existing units bench-tested by a qualified electronics repair facility. Replace any damaged harness sections with proper CAN-rated twisted pair cable, maintaining correct wire routing and shielding. After repairs, clear codes and perform a complete operational test under load.

Disclaimer: This guide provides general troubleshooting information. Complex electrical diagnostics should be performed by qualified technicians with appropriate training and equipment. Always consult official Doosan service documentation and follow proper safety procedures when working on heavy equipment electrical systems.