What is Caterpillar Fault Code 0586?

Caterpillar Fault Code 0586 indicates an abnormal voltage condition in the Engine Speed/Timing Sensor Circuit, specifically detecting a voltage level that is either too high or too low for proper engine operation. This diagnostic trouble code (DTC) signals that the Electronic Control Module (ECM) is receiving irregular signals from the primary speed/timing sensor, which monitors crankshaft position and engine RPM.

This fault is critical for Caterpillar excavators because the speed/timing sensor provides essential data for fuel injection timing, engine speed control, and overall combustion management. When the ECM cannot reliably read engine position and speed, it directly impacts machine performance, fuel efficiency, and may trigger protective shutdown protocols to prevent engine damage.

Common Symptoms

Operators and mechanics typically observe these indicators when Code 0586 is active:

• Engine cranks but fails to start or experiences extended cranking time before ignition
• Check Engine Light or Warning Lamp illuminated on the instrument cluster
• Engine runs rough or stalls intermittently, particularly during idle or load transitions
• Loss of power or inability to reach rated RPM under working conditions
• ECM-initiated derate mode where engine power is significantly reduced as a protective measure

Potential Causes

The most common technical reasons for Code 0586 appearing on used Caterpillar excavators include:

• Damaged or corroded speed/timing sensor connector due to exposure to moisture, hydraulic fluid contamination, or years of vibration
• Worn or broken sensor wiring harness, especially at known rub points near the flywheel housing or engine block mounting areas
• Failed primary speed/timing sensor from normal wear, excessive heat exposure, or internal component breakdown
• Loose sensor mounting causing improper air gap between the sensor tip and crankshaft reluctor ring
• ECM voltage supply issues or internal ECM faults affecting the sensor circuit power
• Damaged reluctor ring teeth on the crankshaft (common in high-hour machines with previous mechanical failures)

How to Troubleshoot and Fix Code 0586

Step 1: Visual Inspection and Connection Check Begin by inspecting the speed/timing sensor located near the flywheel housing. Check the sensor connector for corrosion, bent pins, moisture intrusion, or physical damage. On used excavators, pay special attention to harness routing where wires may have rubbed against metal surfaces over thousands of operating hours. Clean connections with electrical contact cleaner and ensure proper seating.

Step 2: Sensor Resistance and Voltage Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. Typical specifications range between 200-1000 ohms (consult your specific model's service manual). Test the supply voltage at the harness connector with the key on, engine off—you should see approximately 8-12 volts. Compare readings against Caterpillar specifications for your engine model.

Step 3: Air Gap and Physical Condition Assessment Check the air gap between the sensor tip and reluctor ring using a feeler gauge—typical specifications are 0.020-0.050 inches (0.5-1.3mm). Inspect the reluctor ring teeth for damage, missing teeth, or excessive buildup of metallic debris. Rotate the engine manually to verify all teeth are intact.

Step 4: Wiring Harness Continuity Test Perform a continuity test from the sensor connector back to the ECM connector to identify any breaks in the wiring. Check for shorts to ground or shorts to power using the multimeter's resistance function. On used machines, harness damage often occurs where cables pass through grommets or near heat sources.

Step 5: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Caterpillar speed/timing sensor to ensure proper specifications. After installation, clear the fault code using Caterpillar Electronic Technician (Cat ET) diagnostic software and perform a test run. Monitor for code recurrence and verify proper engine operation across all RPM ranges.

---

Disclaimer: This guide provides general troubleshooting information for Caterpillar Fault Code 0586. Always consult the specific service manual for your excavator model and consider professional diagnostic assistance for complex electrical issues or if you lack proper diagnostic equipment.