Repair Info - Emissions Repair Explained
Overview | Component Testing - Doing It Right | Oxygen (O2) Sensor TestingOxygen (O2) Sensor Testing
Emissions repair technicians should be in the habit of checking O2 sensor performance on every vehicle they work on. O2 sensors are critical to controlling emissions, and it is very common for O2 sensors to wear out and fail.
To accurately evaluate the performance of an O2 sensor, the technician must determine the voltage range, response time, and number of cross counts. To do this, the technician will need to perform at least two tests: a snap-throttle test, and a cross-count test. Both use a digital storage oscilloscope (DSO) to monitor voltage over time.
| Test Condition | Specification |
|---|---|
| Table 1: O2 Sensor Performance Criteria | |
| maximum voltage when forced rich |
greater than 900 mV |
| minimum voltage when forced lean |
less than 100 mV |
| maximum response time from lean to rich |
less than 100 ms between 300 mV and 600 mV |
| maximum response time from rich to lean |
less than 100 ms between 600 mV and 300 mV |
| cross counts at 2500 rpm |
at least 5 cross counts in a 10 second period |
