What is XCMG XE4D95 (CM2150C-CM2150D) Fault Code 1677?

Fault Code 1677 indicates a high circuit voltage detected in the Engine Speed/Position Sensor Circuit. This code triggers when the Engine Control Module (ECM) detects an abnormally high voltage signal from the camshaft position sensor or crankshaft position sensor circuit, exceeding the manufacturer's specified threshold of approximately 5 volts.

For the Cummins CM2150C and CM2150D engines found in XCMG XE4D95 excavators, this code is critical because these sensors provide essential timing data to the ECM for fuel injection control and engine synchronization. When this fault is active, the engine may experience performance degradation or fail to start altogether, directly impacting productivity on the job site.

Common Symptoms

• Check Engine Light (CEL) illuminated on the instrument cluster with possible amber warning indicator
• Hard starting conditions or extended cranking time before the engine fires
• Engine derating or reduced power output, limiting hydraulic performance and digging force
• Rough idle or irregular engine operation, particularly noticeable at low RPM
• Complete engine shutdown in severe cases where the ECM cannot establish proper timing reference

Potential Causes

The most common technical reasons for Code 1677 on used XCMG excavators include:

• Damaged or chafed wiring harness along the engine block where vibration causes wire insulation wear, creating short-to-power conditions
• Corroded or moisture-contaminated sensor connectors, especially common in machines operating in wet or humid environments
• Failed camshaft or crankshaft position sensor with internal short circuit conditions
• ECM internal fault or voltage regulation issues within the control module itself
• Aftermarket or incorrect sensor replacement that doesn't meet Cummins OEM specifications
• Harness routing issues from previous repairs that place wires against hot exhaust components

How to Troubleshoot and Fix Code 1677

Step 1: Visual Inspection Begin with a thorough inspection of the sensor wiring harness from the ECM connector to both position sensors. On used excavators, pay particular attention to harness routing near the engine bell housing and timing cover where vibration-induced chafing commonly occurs. Check all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. The camshaft/crankshaft position sensors should typically read between 200-1000 ohms. Next, check for voltage at the harness connector with the key on, engine off—you should see approximately 5 volts supply voltage from the ECM. Any reading above 5.5 volts indicates a circuit problem.

Step 3: Circuit Isolation Disconnect the ECM harness connector and check for continuity between the sensor signal wire and battery positive. Any continuity indicates a short-to-power condition in the harness. For used machines, carefully inspect wire routing through protective looms and grommets, as deteriorated rubber can allow wire-to-metal contact.

Step 4: Component Replacement If harness and connections test normal, replace the affected position sensor with a genuine Cummins part. After replacement on used equipment, always apply dielectric grease to connector terminals to prevent future corrosion. Clear codes using Cummins INSITE diagnostic software or compatible scan tool and perform a test run under load.

Disclaimer: This guide provides general troubleshooting information. Always consult the official XCMG and Cummins service manuals for your specific machine serial number, and consider professional diagnostic assistance for complex electrical issues.