Category
TechASSIST BulletinsDate
August 21, 2025
Exhaust Gas Temperature (EGT) Sensors have become standard on the majority of modern vehicles, including those from leading manufacturers such as Volkswagen Group, Ford, Fiat, BMW, Renault, and Mercedes-Benz. Once a rare sight in the aftermarket, demand for EGT sensor replacements has surged as these components play an increasingly critical role in emission control and engine performance.
This bulletin covers what EGT sensors do, how they work, common causes of failure, symptoms, and key fitting tips for technicians!
What is an Exhaust Gas Temperature Sensor?
An EGT sensor is a thermistor encased in vibration-resistant cement and housed in a high-temperature stainless steel sheath. It’s designed to measure exhaust gas temperatures—often exceeding 900°C—and convert them into a voltage signal for the ECU.
The sensor's resistance changes with temperature. These changes are interpreted by the engine control unit (ECU) to help regulate various emissions systems and engine functions.
What Does an EGT Sensor Do?
EGT sensors serve multiple purposes in both petrol and diesel vehicles. Their core functions include:
- Protecting components such as the DPF, turbocharger, and catalytic converter from overheating
- Supporting emissions control systems like Selective Catalytic Reduction (SCR) and Exhaust Gas Recirculation (EGR)
- Assisting DPF regeneration by monitoring temperature thresholds
- Controlling turbo boost pressure in real-time
The sensor's specific function depends on its location within the exhaust system.
Typical EGT Sensor Locations
Sensor positions vary by vehicle, but common locations include:
- Before and after the turbocharger – To monitor boost temperature. Pre-turbo sensors endure the highest temperatures (up to 900°C), while post-turbo gases cool to around 400–500°C.
- Before and after the DPF – To support regeneration cycles by confirming the correct temperatures for soot combustion (200–400°C).
- Before and after the catalytic converter – To prevent overheating and monitor the SCR process. Gases here are typically around 100–200°C.
Most modern vehicles now feature at least four EGT sensors, especially diesels with advanced emissions systems.
Common Causes of EGT Sensor Failure?
Extreme Heat
Continuous exposure to temperatures nearing 900°C naturally causes wear over time.
Damaged or Broken Wires
EGT sensors can be damaged during unrelated repairs, especially if nearby components like the DPF or exhaust are replaced. Twisted or kinked wires are a frequent issue.
Vibration
While sensors are designed to resist vibration, the constant stress of engine operation can still lead to sensor fatigue or internal fractures over the long term.
Tip: When replacing major exhaust components, it’s good practice to replace the EGT sensors at the same time to avoid future failures and ensure system compatibility.
Symptoms of a Faulty EGT Sensor
Reduced fuel efficiency:
Faulty readings can prolong DPF regeneration or trigger unnecessary cycles, leading to excess fuel usage.
Drivability issues:
Hesitation, power loss, or irregular DPF regeneration events may occur.
Illuminated check engine light:
NTC
NTC (Negative Temperature Coefficient) sensors often trigger an immediate fault code.
PTC
PTC (Positive Temperature Coefficient) sensors can fail more subtly, continuing to send misleading signals that interfere with DPF or SCR function, making diagnosis trickier.
EGT Sensor Fitting Tips
- Always allow the exhaust system to cool fully before starting work.
- Handle sensors with care – dropping them can damage the internal thermistor or its cement fixing.
- Clean the exhaust thread using a suitable cleaning tap before installing threaded sensors.
- Apply copper grease to the thread only – never grease the sensor tip or nose. This helps prevent thread galling and eases removal later.
- Torque to spec – Use an open-ended torque wrench and follow manufacturer guidelines to avoid overtightening or damaging the wires.
- Check system function after installation – Start the engine and ensure proper operation. A fault code reset or ECU adaptation may be necessary.
As vehicles become more emissions-focused, components like EGT sensors are now mission-critical. By understanding their role and following correct diagnostic and installation procedures, independent workshops and factors can confidently meet growing demand and avoid costly comebacks.
For quality aftermarket replacements, ensure you're fitting OE-matching parts supported by robust warranty and technical support.
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Exhaust Gas Temperature Sensors: FAQs
Answers to common questions about EGT sensor symptoms, applications and replacement.
What does an exhaust gas temperature sensor do?
An exhaust gas temperature (EGT) sensor measures temperature in the exhaust system and sends that information to the engine control unit. Depending on its position and the vehicle, its readings help protect exhaust components from overheating and support emissions control, including diesel particulate filter (DPF) regeneration.
Where are EGT sensors fitted?
EGT sensors can be fitted before or after components such as the turbocharger, DPF and catalytic converter. Their number and positions vary by vehicle and engine. Identify the exact sensor position using vehicle-specific information before ordering a replacement.
What are the symptoms of a faulty EGT sensor?
Possible symptoms include an engine warning light, reduced performance, increased fuel consumption and problems with DPF regeneration. These symptoms can have other causes, so diagnosis should confirm the fault before a sensor is replaced.
Can an EGT sensor fault affect DPF regeneration?
Yes. The engine control unit uses exhaust temperature information to help manage regeneration. Incorrect readings can disrupt that process. Follow the vehicle manufacturer’s diagnostic procedure to establish whether the problem is with the sensor, its wiring or another part of the system.
Why do exhaust gas temperature sensors fail?
EGT sensors work in a demanding environment. Heat and vibration can contribute to failure, while wiring can be damaged, twisted or kinked during nearby exhaust repairs. Inspect the sensor wiring and connectors as part of diagnosis.
Are all EGT sensors interchangeable?
No. The correct replacement depends on the vehicle, engine and sensor position. Check application data and the relevant part reference rather than relying on appearance alone. Use the ELTA eCAT to help identify the correct application.
What should I check when fitting a replacement EGT sensor?
Allow the exhaust to cool fully and handle the sensor carefully. Follow the vehicle and sensor manufacturer’s instructions for thread preparation, any approved lubricant, tightening torque and wiring routing. After fitting, carry out the specified diagnostic checks and any required fault-code clearing or adaptation.
Where can I find VXPRO EGT sensors and technical support?
Explore the VXPRO exhaust gas temperature sensor range, check applications in the ELTA eCAT, or contact TechASSIST for technical support with ELTA parts.
For media inquiries, please contact:
Tim Brotherton
Marketing & Communications Manager at ELTA Automotive Ltd