Multi-choice problem: Continue writing the next sentence in this paragraph:

How to change an egr valve
Use a car scan to test the egr valve.
A scan tool reads information from your on-board diagnostics, version ii (obd-ii) system. This system collects information from the sensors in your engine.

Options:
1). The lack of readings may indicate egr valve failure. The observable risk for egr valve failure is that your system may not recognize data from the test.;
2). If the sensor detects something wrong, it reports it as an error code to the obd-ii. A scan tool allows you to read this code.;
3). This can be useful when you run your engine at night, or while you do intermittent repairs. Let your engine run at a constant 100 fahrenheit.;
4). These scans will not only tell you how the different systems work, but can also tell you what your engine detects, and how it relies on these. These scans usually do not show up on your diagnostics panel.;
2).