What is XCMG B3.9-5.9-C8.3 CM2150 Fault Code 697-3?

Fault Code 697-3 indicates a "Coolant Level Sensor Circuit – Voltage Above Normal or Shorted to High Source" in the Cummins CM2150 engine control system used in XCMG excavators. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally high voltage signal from the coolant level sensor circuit, typically exceeding 4.5 volts when the normal operating range is 0.5-4.5V.

This code is critical for XCMG machines because the CM2150 ECM uses coolant level data to prevent catastrophic engine overheating. When this fault is active, the engine may enter a derate mode or display inaccurate coolant level readings, potentially leading to undetected low coolant conditions that could cause engine damage or complete failure during operation.

Common Symptoms

• Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) illuminated on the dashboard
• Coolant level gauge reading full constantly, even when coolant is actually low
• Engine derate or reduced power output as a protective measure
• Audible warning alarms or messages indicating coolant system faults
• In severe cases, the ECM may prevent engine start or force an immediate shutdown

Potential Causes

The most common technical causes for Code 697-3 in used XCMG excavators include:

• Damaged or corroded wiring harness near the coolant reservoir, especially at pinch points where the harness routes near the engine block or frame rails
• Shorted coolant level sensor internal failure causing constant high voltage output
• Corroded or moisture-contaminated connector pins at the sensor or ECM interface (common in machines with 3,000+ operating hours)
• Chafed wiring rubbing against metal surfaces, creating an intermittent short to battery voltage
• Faulty ECM (less common, but possible in high-hour machines with environmental exposure)
• Aftermarket wiring repairs or modifications that created improper grounding or voltage routing

How to Troubleshoot and Fix Code 697-3

Step 1: Visual Inspection Begin with a thorough inspection of the coolant level sensor located on the coolant reservoir/expansion tank. Check the sensor connector for corrosion, bent pins, or moisture intrusion. On used excavators, pay special attention to the wiring harness routing from the sensor to the ECM—look for signs of rubbing, cracking, or exposure to heat sources.

Step 2: Electrical Testing Disconnect the coolant level sensor connector. Using a digital multimeter (DMM), measure the voltage at the ECM side of the harness with the ignition on. You should see approximately 5 volts (reference voltage from ECM). If voltage reads above 5.5V or fluctuates, inspect for a short to battery voltage in the harness. Next, check circuit resistance with ignition off—readings should be within 100-300 ohms for the sensor circuit.

Step 3: Component Testing and Replacement Test the coolant level sensor itself by measuring its resistance while simulating float positions. Replace the sensor if readings are out of specification (consult Cummins CM2150 service manual for exact values). If the sensor tests good, the issue is likely in the wiring harness. For used machines, replace any sections of harness showing wear, and apply dielectric grease to all connectors. Use Cummins INSITE diagnostic software to clear codes and verify the repair before returning the machine to service.

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Disclaimer: This guide provides general troubleshooting information. Always consult the manufacturer's service manual and consider professional diagnosis for complex electrical issues. Improper repairs can cause further damage or safety hazards.