The exhaust gas temperature sensor, or EGT sensor, measures how hot the exhaust is at key points in the system. The computer uses these readings to protect expensive parts like the turbocharger, catalytic converter, and diesel particulate filter from overheating, and to manage regeneration on diesels.
Animated: how a Exhaust Gas Temperature Sensor actually works
🔧 How It Works, Step by Step
1
Tip senses heat
The sensor tip sits in the exhaust stream and responds to temperature.
2
Resistance changes
The sensing element changes resistance as the exhaust gets hotter or cooler.
3
Signal sent to ECU
The changing signal tells the computer the exact exhaust temperature.
4
System responds
The computer adjusts fueling, turbo boost, or regeneration to protect parts.
5
Overheating prevented
If temperatures climb too high, the computer takes action to protect components.
🧩 The Key Parts
Sensing element
Changes resistance with exhaust temperature.
Probe tip
Sits in the gas stream to read heat directly.
Signal wiring
Carries the temperature reading to the computer.
Mounting boss
Positions the sensor at the critical point in the system.
📋 Free OBD2 Code Cheat Sheet
The 50 most common check engine codes with likely cause and DIY fix cost. Sent once.
🩺 Signs of a Failing Exhaust Gas Temperature Sensor
Check engine light with EGT sensor codes
Reduced power or limp mode
Regeneration problems on diesels
Poor fuel economy
Failed emissions test
Turbo protection derate
⚠️ Common Problems
Heat degradation
Constant extreme heat degrades the element, causing drift or failure.
Wiring damage
Broken or corroded wiring near the hot exhaust interrupts the signal.
Contamination
Soot buildup on the tip slows the reading and skews temperature control.
💰 Cost to Fix
$150-$500typical range to repair or replace, parts and labor
❓ FAQ
What does an EGT sensor protect?
It guards the turbocharger, catalytic converter, and diesel particulate filter from damaging overheating by feeding temperature data to the computer.
Can a bad EGT sensor cause limp mode?
Yes. If the computer cannot trust exhaust temperature, it may reduce power to protect components until the sensor is fixed.
How many EGT sensors does a diesel have?
Modern diesels often use several, placed before and after the turbo, converter, and DPF to manage heat and regeneration.