Exhaust Gas Temperature Sensor Types and What You Need to Know

Exhaust Gas Temperature Sensors (EGTS) are critical components in modern vehicles, particularly for diesel engines. These sensors measure the temperature of exhaust gases and play a vital role in ensuring engine efficiency, preventing overheating, and maintaining emission standards. This guide provides an overview of EGTS, their types, locations, and functions.

What is an Exhaust Gas Temperature Sensor (EGTS)?

An Exhaust Gas Temperature Sensor is a monitoring device that measures the temperature of exhaust gases in a vehicle’s exhaust system. By continuously transmitting voltage signals to the Engine Control Unit (ECU), the sensor helps monitor overall engine and exhaust conditions. This enables the ECU to:

• Take corrective actions, such as reducing engine power to prevent overheating.
• Alert the driver to potential issues, like low component efficiency.

EGTS are also instrumental in aftertreatment processes, ensuring harmful gases are reduced effectively to comply with emission regulations.

Types of Exhaust Gas Temperature Sensors

There are two primary types of EGTS technologies:

1. PTC (Positive Temperature Coefficient) EGT Sensors

• How They Work:
  • Resistance increases as temperature rises.
  • Resistance variation follows a linear scale.
• Specifications:
  • Temperature range: -70°C to 900°C.
  • Utilizes PT200 sensing elements constructed via thin-film processes.
  • At 0°C, resistance is typically 200Ω (Ohms), enabling precise temperature detection.
• Applications:
  • Suitable for areas requiring accurate linear readings over a wide temperature range.

2. NTC (Negative Temperature Coefficient) EGT Sensors

• How They Work:
  • Resistance decreases as temperature rises.
  • Resistance variation follows a logarithmic (log) scale.
• Specifications:
  • Temperature range: -40°C to 900°C, depending on thermistor type.
  • Constructed via press-forming processes with embedded conductors.
  • Highly sensitive to minor temperature variations.
• Applications:
  • Ideal for applications requiring rapid responses to temperature changes.

Locations and Functions of EGTS

EGTS are strategically placed throughout the exhaust aftertreatment system, each with specific monitoring and protective functions.

1. Before and After the Turbocharger

• Function:
  • Monitors turbocharger temperature to ensure proper operation (150°C to 200°C).
  • Detects overheating to prevent component damage.

2. Before and After the Diesel Oxidation Catalyst (DOC)

• Function:
  • Monitors entry temperature (minimum 200°C) to ensure DOC activation.
  • Detects component health issues, such as clogging or overheating.

3. Before and After the Diesel Particulate Filter (DPF)

• Function:
  • Monitors the DPF regeneration process to ensure its effectiveness.
  • Tracks component health, identifying potential clogging or overheating.

4. Before and After the Selective Catalytic Reduction (SCR) System

• Function:
  • Monitors exhaust gas entry temperature (200°C to 400°C) for SCR activation.
  • Ensures exit gases meet emission standards after proper treatment.

Why is EGTS Maintenance Important?

• Prevents Overheating:
  • Overheating can cause irreversible damage to vehicle components.
• Enhances Engine Efficiency:
  • EGTS data ensures optimal engine performance and fuel efficiency.
• Supports Emission Standards:
  • Properly functioning sensors ensure aftertreatment systems effectively reduce toxic emissions.
• Avoids Costly Repairs:
  • Regular maintenance prevents damage to components like turbochargers, DOCs, and DPFs.

Conclusion

Exhaust Gas Temperature Sensors are essential for monitoring and maintaining the health of a vehicle’s exhaust system. By accurately detecting temperature variations, EGTS help prevent overheating, improve engine performance, and ensure compliance with emission regulations. Regular maintenance and understanding the role of these sensors can significantly enhance vehicle longevity and reduce environmental impact.

‍