Exhaust gas temperature sensors on HGVs: where they fail and why
Modern HGV aftertreatment systems use multiple temperature sensors positioned along the exhaust path. Sensors are typically located before and after the DPF, before and after the SCR catalyst, and at the turbo outlet. The ECU uses the temperature differential across each component to determine whether the DPF is regenerating correctly and whether the SCR catalyst is at the right temperature for AdBlue dosing.
Sensor failures are common on high-mileage vehicles. The most frequent causes are connector corrosion from road moisture, physical damage to the sensing element from heat cycling, and cable chafing where the sensor lead runs close to the exhaust. Before replacing a sensor, clean the connector and check the resistance value against the manufacturer's specification. Use anti-seize compound on the threads of any replacement sensor.
Frequently Asked Questions
How do I know which exhaust temperature sensor has failed on my HGV?
A diagnostic scan will identify the specific sensor circuit with the fault code. HGV aftertreatment systems typically have four or more temperature sensors, each with an individual sensor identifier in the fault code. The scan will point you to the sensor location, described by its position relative to the aftertreatment components.
Can a faulty exhaust temperature sensor cause engine derating?
Yes. If the ECU cannot confirm safe operating temperatures in the aftertreatment system, it will derate the engine or restrict performance as a protective measure. Resolving the temperature sensor fault usually restores full engine performance.
Do I need to recalibrate the sensor after fitting?
No. Exhaust temperature sensors are not calibrated items. Fitting a replacement of the correct specification and clearing the fault codes is sufficient.
Does Truckstop Group stock exhaust temperature sensors for all HGV makes?
We stock EGT sensors for DAF, Scania, Volvo, MAN, Mercedes-Benz, Iveco, and Renault. Call us on 01527 598 000 with your chassis number and fault code if you need help identifying the correct sensor.
