The Exhaust Gas Temperature sensor is a thermistor element fixed in cement to protect from vibration and housed in stainless steel to withstand extreme temperatures of up to 900°C.
Changes in temperature result in changes in resistance of the sensor and this is communicated to the ECU as a voltage.
In a TechAssist bulletin, Lucas explain that these sensors protect vital exhaust components from overheating and help to control emissions.
They are also used in several combustion control processes in both diesel and petrol engines including selective catalytic reduction (SCR), turbo boost, exhaust gas recirculation and DPF regeneration.
A faulty sensor communicating incorrect voltages can result in poor fuel efficiency because the DPF regeneration takes longer to complete.
DPF regeneration
The DPF regeneration process can affect driveability.
Faulty exhaust gas temperature sensors can lead to unnecessary regenerations causing inconvenience for the driver.
Lucas say that some sensors are harder to diagnose than others.
PTC-type sensor failures are often misdiagnosed as DPF issues as after failure they continue to function sending incorrect signals to the ECU affecting the DPF regeneration process.
NTC-type sensors are more likely to trigger the engine check light on failure.
Extreme heat is often a cause of failure over time.
Lucas say a common problem with all wired sensors is that wires can break, especially if subjected to harsh twists and turns.
They are also easily damaged when replacing other components in the exhaust system.
As a result Lucas recommend that exhaust sensors are replaced at the same time as the exhaust system or components such as the DPF or CAT.
Exhaust Gas Temperature sensors have many features to help them withstand vibration but it can still take its toll over time.
Installation advice
1. Ensure the exhaust system is cool before starting work.
2. Handle the exhaust gas temperature sensor carefully, dropping the component may cause unseen damage to the cement that secures the thermistor.
3. If the sensor is threaded, clean the thread in the exhaust pipe with a cleaning tap.
4. Apply copper grease on the sensor thread only. Although some sensors are pre-greased, extra grease will prevent thread galling and reduce friction which could lead to over torque (especially with stainless steel thread.)
5. Tighten the sensor to the required torque as prescribed by the VM, using an open-ended torque wrench to avoid over-tightening and/or damage to the wire.
6. Turn the engine on and check if the exhaust system works properly. A reset of the ECU may be required.
From just 100 part numbers, Lucas Electrical’s exhaust gas temperature sensor range covers over ten million vehicles on the road.
To find out more about and to view Lucas Electrical’s range of exhaust gas temperature sensors, select ‘more details’ below.
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