What is XCMG XE750D Fault Code 168-4 SPN168 FMI4?

Fault Code 168-4 (SPN 168, FMI 4) indicates a battery voltage circuit problem with voltage below normal or shorted to ground. This code specifically monitors the electrical system's ability to maintain proper voltage supply to the Engine Control Module (ECM) and critical electronic components on the XCMG XE750D excavator.

SPN 168 refers to the battery voltage circuit, while FMI 4 designates voltage below normal or shorted low. This fault directly impacts the machine's ability to maintain consistent power delivery to sensors, solenoids, and control modules. On heavy-class excavators like the XE750D, stable electrical voltage is critical for proper fuel injection timing, hydraulic system control, and emissions system operation. Voltage irregularities can cause erratic machine behavior and potential component damage.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator illuminated on the dashboard
• Engine power derate or reduced performance mode to protect electronic components
• Difficult starting or extended cranking times, especially during cold starts
• Intermittent electrical failures including gauge flickering or display screen resets
• Hydraulic system irregularities due to solenoid valve malfunction from insufficient voltage

Potential Causes

The most common technical causes for Code 168-4 on used XCMG excavators include:

• Failing alternator unable to maintain 24-28V charging voltage under load
• Degraded battery bank with one or more batteries showing reduced capacity or internal cell failure
• Corroded battery terminals or cables creating excessive resistance in the charging circuit
• Damaged wiring harness between alternator and ECM, particularly at flex points near the engine mount
• Faulty voltage regulator within the alternator assembly
• Parasitic electrical drain from aftermarket accessories or damaged components
• Loose or corroded ground connections at the engine block or frame rails

How to Troubleshoot and Fix Code 168-4

Step 1: Perform Visual Inspection Inspect all battery terminals and cable connections for corrosion, looseness, or damage. On used excavators, check for cable fraying where harnesses contact the frame. Clean terminals with a wire brush and apply dielectric grease.

Step 2: Test Battery Voltage Using a digital multimeter, measure battery voltage with the engine off (should read 24-26V for dual 12V system). Start the engine and verify charging voltage reaches 27-28V at idle. If voltage remains below 26V during operation, suspect alternator failure.

Step 3: Load Test Battery Bank Perform a load test on each battery individually. Replace any battery showing less than 12.4V resting voltage or failing to maintain voltage under 200-amp load for 15 seconds.

Step 4: Inspect Alternator and Wiring Check alternator belt tension and inspect for glazing. Trace the main power wire from alternator to ECM, checking for chafing at known rub points near the hydraulic pump mounting area. Measure ground circuit resistance (should be below 0.5 ohms).

Step 5: Check for Parasitic Draw With engine off, use an amp clamp meter on the positive battery cable. Draw exceeding 50mA indicates a parasitic drain requiring circuit-by-circuit isolation.

For used machinery, always inspect connector seals for moisture intrusion and harness routing for modifications that may cause voltage drops.

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Disclaimer: This guide provides general troubleshooting information. Always consult the XCMG service manual and qualified diesel technicians for complex electrical diagnostics. Improper electrical work can cause equipment damage or safety hazards.