What is Sany SY6HK1 Fault Code P0122(43)?

Fault Code P0122(43) indicates a Throttle Position Sensor (TPS) Circuit Low Input voltage condition on the Sany SY6HK1 excavator. This diagnostic trouble code means the Engine Control Module (ECM) is receiving a voltage signal from the throttle position sensor that is below the manufacturer's specified threshold, typically under 0.5 volts when a higher reading is expected.

The TPS is critical for this machine's performance because it communicates the throttle pedal position to the ECM, which then calculates proper fuel delivery, engine speed control, and hydraulic pump output. On the SY6HK1 model, which often uses Isuzu or Yanmar diesel powerplants, this sensor directly impacts engine responsiveness and prevents the excavator from operating efficiently under load. When the ECM detects abnormally low voltage from this circuit, it triggers P0122(43) and may implement engine derate to protect components.

Common Symptoms

• Check Engine Light (CEL) or malfunction indicator lamp illuminated on the instrument cluster
• Reduced engine power or noticeable lack of throttle response, especially during swing or digging operations
• Engine operating in limp mode, limiting RPM to 1200-1500 range regardless of pedal input
• Erratic idle or engine stalling when attempting to increase throttle
• Hydraulic system sluggishness due to inadequate engine speed for pump demand

Potential Causes

The most common technical causes for P0122(43) on used Sany excavators include:

• Faulty throttle position sensor – Internal potentiometer wear or failure, particularly common after 4,000+ operating hours
• Damaged wiring harness – Chafing or breaks in the TPS signal wire, especially near the engine firewall where vibration causes wire-to-frame contact on SY6HK1 models
• Corroded or loose connector pins – Moisture intrusion at the TPS connector (3-pin weatherpack style) causing high resistance or open circuits
• Poor ground connection – Deteriorated ground strap between sensor and engine block
• Short to ground in the signal circuit, often found where harnesses route near sharp metal edges
• ECM internal fault (rare) – Failed input circuitry within the engine control module

How to Troubleshoot and Fix Code P0122(43)

Step 1: Visual Inspection Begin by locating the throttle position sensor mounted on the fuel injection pump or throttle body. Inspect the 3-pin connector for corrosion, bent pins, or moisture. On used excavators, check the entire wiring harness routing from the TPS to the ECM for abrasion points, particularly where it passes through bulkheads or contacts the engine block. Look for greenish corrosion or oil contamination on connectors.

Step 2: Electrical Testing Using a digital multimeter (DMM), backprobe the TPS connector with the ignition ON, engine OFF. Measure the reference voltage (typically 5 volts) on the supply wire. Check the signal wire voltage – it should read between 0.5-4.5 volts depending on throttle position. If reading is consistently below 0.3 volts, suspect sensor failure. Perform a continuity test on the signal wire back to the ECM with the connector disconnected; resistance should be less than 5 ohms.

Step 3: Ground Circuit Verification Test the ground circuit resistance between the TPS ground pin and battery negative – should read less than 1 ohm. Clean all ground connection points with a wire brush and apply dielectric grease.

Step 4: Component Replacement If voltage tests confirm sensor failure, replace the throttle position sensor with an OEM or quality aftermarket unit. For used machines, simultaneously replace the connector pigtail if any corrosion exists. After installation, clear codes using Sany diagnostic software or a compatible J1939 scan tool, then perform a TPS relearn procedure per manufacturer specifications.

Step 5: Post-Repair Verification Cycle the ignition and monitor live data to confirm TPS voltage ranges from approximately 0.7V (idle) to 4.5V (full throttle). Perform a loaded operational test to ensure proper engine response.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific serial number and consider professional diagnostics if you're unfamiliar with electrical testing procedures. Improper repairs can cause additional damage or safety hazards.