What do you do when your multi-meter shows voltage and ground, and the NOx sensor wiring harness shows no sign of damage? Take a look at this quick fix where a lab-scope was used to take a deeper dive into the cause of an erratic NOx sensor parameter.
Vehicle
2015 Skoda Yeti 2.0 Diesel
Title
P20EE, Replaced NOx Sensor
Complaint
The customer states the check engine light is on.
Cause
Connected a scan tool and found code P20EE – NOx Catalytic Converter System Efficiency Below Threshold (Bank 1). Performed a road test, used the scan tool to monitor live data and found the NOx sensor signal parameter was erratic. Visually inspected the NOx sensor wiring harness, and found no obvious signs of damage. Disconnected the NOx sensor connector, visually inspected the connector and terminals, and found no obvious signs of damage. With key on, engine off, using a multi-meter, checked for voltage and ground at the NOx sensor connector and found both were present. Backprobed the NOx sensor, ran the engine, monitored the sensor signal on a lab scope and found the NOx sensor signal observed on the lab scope intermittently dropped out. The results of these tests verified the NOx sensor
Correction
Replaced the NOx sensor, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned
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