2013 Hino 338
I'm trying to get good at diagnosing bad NOx sensors. Sometimes it's obvious, like it's completely dead. But often, one may be giving a bad reading.
1) Monitoring "NOx sensor request state". Under what conditions does the NOx sensor request state change from "Not requested" to "Requesting"? I'm pretty sure something has to get up to temperature before the sensors will read. The state goes back and forth between "Not requested" to "Requesting". Shouldn't it always be watching the NOx readings to decide when to dose DEF?
2) When in the DCU is in the "Requesting" state (reading the NOX sensors) and I'm monitoring NOx density form the Fore and Rear NOx sensors. The NOx readings usually fluctuate from 0 to 500 ppm. But sometimes one sensor, or both sensors will jump to something like 65,000 ppm for a few seconds. Is this normal? I've monitored this on 2 trucks and the both do this. One truck had no SCR faults.
3) What is the normal ppm range of these sensors?
4) By monitoring the NOx densities of both sensors, how do I determine if a sensor is giving bad readings, other than obvious things like being completely dead?
I'm trying to get good at diagnosing bad NOx sensors. Sometimes it's obvious, like it's completely dead. But often, one may be giving a bad reading.
1) Monitoring "NOx sensor request state". Under what conditions does the NOx sensor request state change from "Not requested" to "Requesting"? I'm pretty sure something has to get up to temperature before the sensors will read. The state goes back and forth between "Not requested" to "Requesting". Shouldn't it always be watching the NOx readings to decide when to dose DEF?
2) When in the DCU is in the "Requesting" state (reading the NOX sensors) and I'm monitoring NOx density form the Fore and Rear NOx sensors. The NOx readings usually fluctuate from 0 to 500 ppm. But sometimes one sensor, or both sensors will jump to something like 65,000 ppm for a few seconds. Is this normal? I've monitored this on 2 trucks and the both do this. One truck had no SCR faults.
3) What is the normal ppm range of these sensors?
4) By monitoring the NOx densities of both sensors, how do I determine if a sensor is giving bad readings, other than obvious things like being completely dead?