What is XCMG XE6D125-6D140-6D170-CM850-CM2850 Fault Code 248?

Fault Code 248 indicates an Engine Oil Pressure Sensor Circuit Low Voltage condition in XCMG excavators equipped with Cummins CM850/CM2850 engines. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormally low voltage signal from the oil pressure sensor circuit, typically below 0.5 volts when the engine is running.

This fault is critical because the ECM relies on accurate oil pressure data to protect internal engine components from catastrophic damage. When Code 248 is active, the engine may enter derate mode or trigger automatic shutdown protocols, directly impacting machine productivity and potentially masking genuine low oil pressure conditions that could destroy the engine.

Common Symptoms

• Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) illuminated on the instrument cluster
• Engine power derate to 50-75% of rated output, limiting digging force and travel speed
• Oil pressure warning light may activate intermittently or remain constantly illuminated
• Rough idle or hesitation during throttle application as the ECM compensates for unreliable sensor data
• Automatic engine shutdown in severe cases, particularly in machines with strict protection parameters enabled

Potential Causes

The most common technical failures triggering Code 248 in used XCMG excavators include:

• Oil pressure sensor internal failure – Sensor element degradation from heat cycling and contamination (common after 5,000+ hours)
• Damaged sensor wiring harness – Chafing against engine block near the sensor mounting location, a known wear point on XE6D models
• Corroded or loose connector pins at the sensor or ECM interface, especially in machines operated in high-moisture environments
• Short to ground in the signal wire between sensor and ECM, often from pinched harness during previous repairs
• Failed ECM internal circuitry (rare) – Sensor supply voltage regulator malfunction within the engine controller

How to Troubleshoot and Fix Code 248

Step 1: Visual Inspection and Connector Check Begin by inspecting the oil pressure sensor located on the engine block's oil gallery. Check for physical damage, oil contamination on the connector, or evidence of harness rubbing. Clean connector terminals with electrical contact cleaner and verify the locking tab engages properly. On used excavators, corrosion inside connectors is a frequent culprit.

Step 2: Voltage and Resistance Testing Using a digital multimeter (DMM), backprobe the sensor connector with the key on, engine off. Verify 5-volt reference supply from the ECM. Check sensor ground continuity (should be <1 ohm to battery negative). Measure signal wire voltage with engine running at operating temperature – it should read 0.5-4.5 volts depending on actual oil pressure.

Step 3: Signal Wire Continuity and Replacement Disconnect both ends of the harness and test for continuity between sensor and ECM pins (consult wiring diagram). Check for resistance to ground (should be >10k ohms). If wiring passes tests but symptoms persist, replace the oil pressure sensor with OEM-equivalent parts. For used machines, always inspect harness routing for previous damage or improper repairs that may cause intermittent faults.

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