What is XCMG B3.9-5.9-C8.3 CM2150 Fault Code 1073-3?

Fault Code 1073-3 indicates a voltage warning condition in the Engine Position Sensor 1 (Crankshaft Position Sensor) circuit on Cummins CM2150 engines used in XCMG excavators. This code specifically signals that the ECM (Engine Control Module) has detected an abnormal voltage level in the crankshaft position sensor circuit—typically a voltage reading that falls outside the expected range but hasn't completely failed.

The crankshaft position sensor is critical for engine timing, fuel injection synchronization, and overall engine management. When this sensor circuit shows voltage irregularities, the ECM struggles to accurately determine engine speed and piston position, which can lead to poor performance, rough running, or even engine shutdown protection modes. For XCMG machines equipped with Cummins B3.9, 5.9, or C8.3 engines using the CM2150 electronic control system, this fault can significantly impact jobsite productivity.

Common Symptoms

• Check Engine Light illuminated on the instrument panel with possible amber warning indicator
• Rough idle or intermittent engine stumbling, especially during cold starts or low RPM operation
• Hard starting conditions or extended cranking time before the engine fires
• Engine derate mode activation, limiting maximum RPM or power output to protect the engine
• Intermittent stalling or unexpected engine shutdown, particularly on older machines with harness wear

Potential Causes

The most common technical causes for Code 1073-3 on used XCMG excavators include:

• Damaged or corroded wiring harness at the crankshaft position sensor connector, particularly where the harness routes near the engine block or experiences vibration
• Failing crankshaft position sensor with internal resistance degradation due to heat cycles and age
• Contaminated sensor connector pins from oil seepage, dirt intrusion, or moisture accumulation common in construction environments
• Chafed wiring where the sensor harness contacts the engine bellhousing or frame components—a known wear point on high-hour machines
• Intermittent ground connection issues in the sensor circuit return path
• ECM connector corrosion at pins related to the crankshaft sensor input circuit

How to Troubleshoot and Fix Code 1073-3

Step 1: Visual Inspection Begin with a thorough physical examination of the crankshaft position sensor and its wiring harness. On used excavators, carefully inspect the harness routing from the sensor (located near the flywheel housing or front timing cover) to the ECM. Look for abraded insulation, oil contamination, or harness contact points with hot engine components. Check the sensor connector for bent pins, corrosion (green/white deposits), or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, disconnect the crankshaft position sensor connector and measure resistance across the sensor terminals. Typical resistance values for these sensors range from 150-1000 ohms (consult your specific Cummins service manual for exact specifications). Next, check the wiring harness continuity from the sensor connector back to the ECM pins. Measure resistance on each wire—readings should be less than 5 ohms, indicating good conductivity.

Step 3: Voltage Supply Check With the ignition on but engine off, check the supply voltage at the sensor connector. The CM2150 system typically provides 5-volt or 8-volt reference voltage to the sensor. Voltage outside the 4.5-5.5V range (or 7.5-8.5V depending on sensor type) indicates a wiring issue or ECM problem.

Step 4: Advanced Diagnostics Connect Cummins INSITE diagnostic software to read live sensor data and freeze frame information. Monitor the crankshaft position sensor signal while cranking the engine. Erratic voltage patterns or dropouts confirm sensor or wiring issues. For used equipment, pay special attention to connector seal integrity—replace any damaged Deutsch or AMP connectors with OEM parts to prevent recurring issues.

Step 5: Component Replacement If testing confirms sensor failure, replace the crankshaft position sensor with a genuine Cummins part. When installing, apply dielectric grease to connector pins and ensure proper harness routing away from heat sources. Clear the fault code using diagnostic software and perform a test run under load.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Cummins and XCMG service manuals for your specific engine serial number. Complex electrical diagnostics should be performed by qualified diesel technicians with proper diagnostic tools. Improper repairs may cause engine damage or safety hazards.