Long Term Fuel Trim and Short Trim Fuel Trim
Long and short-term fuel trim are very useful indicators of engine performance relative to the manufacturer’s specifications, but before we get into what they tell you, we’ll go over what they are.
Diagnostics
Testing Oxygen Sensors
There are a few different tests for oxygen sensors (also known as lambda sensors), some of which can be run without dedicated tools. The most effective tests tend to be done under normal operating conditions, on a sensor installed on an engine system, though there are some tests which can be done off-vehicle.
How to Test Glow Plugs
Glow plugs are installed on many diesel engines to help with cold starts. They usually fail because of corrosion, overheating, mechanical damage, or metal fatigue, and their failure can cause a variety of problems. The easiest way to test a glow plug is by using a clamp-meter, though digital multimeters can also do the job, and glow-plug testers also work.