Aftermarket March 2022

Fig 1 MARCH 2022 AFTERMARKET 41 www.aftermarketonline.net alone. Garages need to look for slow response times, output range and heater function. Contaminants from poor quality oils and fuel which remain in the exhaust gases can become deposited on the sensor element affecting its operation. Even coolant from a leaking head gasket can reach the element.” Mark added: “The company has a variety of other sensors to satisfy UK requirements including NTK camshaft and crankshaft sensors, a range of 87 NTK mass air flow (MAF) sensors and 69 manifold absolute pressure (MAP) sensors, and exhaust gas temperature (EGT) sensors, with 38-part numbers covering 33 million cars. Links to NGK’s improved PartFinder website can be accessed from its BoxClever App’s homepage.” For more information visit: www.ngkntk.com/uk HELLA technical advice Getting into specifics, and explaining how to check the exhaust gas temperature sensor on a Volkswagen Passat 2.0 TDI, HELLA Product and Brand Manager Matthew Smart said: “Depending on the vehicle, up to four exhaust gas temperature sensors can be installed. The ECU monitors the temperature before the catalytic converter, turbocharger and also upstream and downstream of the DPF. “In vehicles without a selective catalytic reduction (SCR) catalytic converter, the exhaust gas temperature sensor behind the DPF is not required. In the event of a defective exhaust gas temperature sensor, or implausible output values, the system switches to emergency operation or uses a substitute value to protect relevant components from overheating. An error entry is then recorded in the ECU and the warning lamp in the dashboard is activated (see Fig.1) “Errors stored in the memory of the ECU can be replaced by using a suitable diagnostic tool, such as a Hella Gutmann mega macs device. Depending on the system, additional parameters can be displayed and used for troubleshooting (see Fig.2). In this case study the error codes 15709 and 5257 were displayed, which indicate a fault in exhaust gas temperature sensor three. “In this function, the current measured values of the sensor in the ECU can be displayed and evaluated (see Fig.3) In this case we see a vehicle with three exhaust gas temperature sensors, with sensor three displaying a value of -40°, possibly due to an interruption in the electrical wiring or defect in the sensor. System specific circuit diagrams can also be taken from vehicle information and used for troubleshooting purposes (see Fig.4). A visual inspection of the components and peripherals should be carried out after the ECU diagnosis and the sensor should be replaced if the connecting cable or sensor housing is damaged.” Matthew added: “If the threads of the exhaust gas temperature sensors are coated, they must not be treated with an extra coating of hot thread paste and they must be tightened to the torque value specified by the vehicle manufacturer. As a guide, for a HELLA exhaust gas temperature sensor, a torque of 40 - 45 Nm is recommended.” For more information, visit: www.hella.com/techworld/uk/Technical/Sensors- and-actuators/Checking-the-exhaust-gas- temperature-sensor-58074/ Fig 2 Fig 3 Fig 4