What is XCMG XE490D (CM2150 C/D) Fault Code 1658?

Fault Code 1658 indicates an "Intake Air Heater Relay Circuit - Voltage Above Normal or Shorted to High Source." This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects abnormally high voltage in the intake air heater relay circuit, typically above 4.8 volts when the system should be off or grounded.

The CM2150 series ECM monitors this circuit continuously to ensure proper cold-start performance. The intake air heater (also called grid heater) warms incoming air during cold weather starts, reducing white smoke and improving combustion efficiency. When voltage readings exceed normal parameters, the ECM logs Code 1658 and may disable the heater function to prevent electrical damage or component failure.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the dashboard
• Hard starting or extended cranking in cold weather conditions (below 40°F/4°C)
• Excessive white or gray smoke during cold starts due to incomplete combustion
• Loss of intake air heater function with no grid heater operation audible during key-on sequence
• Possible engine derate in severe cases, limiting power output to protect the engine

Potential Causes

The most common technical causes for Code 1658 on used XCMG excavators with Cummins CM2150 engines include:

• Damaged or chafed wiring harness between the ECM and intake air heater relay, especially at engine mounting points or harness routing areas
• Failed intake air heater relay with internal short circuit causing continuous high-side voltage
• Corroded or moisture-contaminated connectors at the relay socket or ECM interface (common in machines operating in wet environments)
• Shorted intake air heater element creating backfeed voltage through the circuit
• ECM internal driver circuit failure (less common, but possible in high-hour used machines)
• Improper previous repairs or aftermarket relay installation with incorrect voltage specifications

How to Troubleshoot and Fix Code 1658

Step 1: Visual Inspection Perform a thorough inspection of the intake air heater relay (typically located in the engine compartment fuse/relay box) and associated wiring. Check for corroded terminals, burnt relay contacts, or damaged wire insulation. On used excavators, pay special attention to harness wear points where cables contact the engine block or frame rails.

Step 2: Electrical Testing Using a digital multimeter (DMM), disconnect the intake air heater relay and measure voltage at the relay socket with key on, engine off. The control side should read battery voltage (12V) when commanded on, and near 0V when off. Check for short-to-power conditions by measuring resistance between the relay control wire and battery positive—readings below 10,000 ohms indicate a short circuit.

Step 3: Component Testing Test the intake air heater relay itself by checking coil resistance (typically 70-100 ohms) and verifying proper switching operation. Replace if resistance is out of specification. If the relay tests good, inspect the grid heater element for internal shorts by measuring resistance across terminals (should be 0.08-0.12 ohms for CM2150 applications).

Step 4: Advanced Diagnostics Connect Cummins Insite or compatible diagnostic software to read freeze frame data and monitor live circuit voltage. Command the heater on/off while monitoring voltage response. If voltage remains high regardless of ECM commands, trace the circuit for short-to-power conditions or replace the ECM harness connector.

Critical Note for Used Equipment: Before replacing expensive components like the ECM, thoroughly inspect all connectors for corrosion, bent pins, or moisture intrusion—these issues are exponentially more common in older machines and often mimic component failures.

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Disclaimer: This guide provides general troubleshooting information. Always consult the manufacturer's service manual and qualified diesel technicians for complex electrical diagnostics. Improper repairs may cause additional damage or safety hazards.