The investment of an oscilloscope to help with the complex job of accurately diagnosing problems in today’s vehicles has really opened up new avenues. Often components are condemned as faulty by the observations made using a serial diagnostic tool (scan-tool) or to a lesser extent a digital multi meter. This alone can lead to costly misdiagnosis.

On a petrol engine at idle (850 RPM) the sequential fuel injectors are firing an average of 8 times per second. Consider that a scan-tool often, will only refresh the displayed data about 4 times per second. It is clear that an awful lot of events can take place & go un noticed when viewed on the scanner alone!

Here are some captures that I have found interesting & enlightening

O2 sensor vs Injector duration