Diagnose car problems without going to a mechanic with an auto code reader. Simply plug it into the car's computer system, then interpret the trouble code readout.
Plug your code reader into the diagnostic link connector under the dash (engine off). Then start the vehicle and follow the code reading procedure in the instruction manual.
Nothing can knock your day off track faster than a “Check Engine” light popping up on your dash. You wonder if you should pull over and shut off your vehicle or drive right to a shop. A code reader/scanner can help you make the drive/no drive decision and even help you fix the problem. It works by plugging into the car's computer system and displaying a “trouble code.”
A code reader/scanner is worth buying if you're a fairly competent amateur mechanic who understands how an engine works. But it's not a silver bullet that will always tell you exactly what's wrong. It'll give you a head start, but you'll still have to do some detective work before you start pulling and replacing parts (more on this later).
The least expensive units are simple code readers that burp up an alphanumeric trouble code but no information about what it means. You'll have to look up the code in a reference book or search the Internet. Midpriced units actually display the problem on the screen, like “P0115 Engine Coolant Temperature Circuit Malfunction.” One model even accesses the Internet, so you can upload the trouble code to a Web site that has information on the most likely cause of the problem.
But if you're a true grease monkey, go for a more expensive scanner. A scanner gives you real-time “live” information so you see the same data your car's computer is seeing. That saves you the hassle of diving under the hood (with a wiring diagram in hand), piercing wires and taking sensor readings.
Code reading and scanning sound
simple, right? Well, there's more to it
than that. A code that indicates your
oxygen sensor is “lean” can mean the
sensor is dead, or it can mean that the
air/fuel mixture really is lean and
you've got either a vacuum leak or a
fuel problem. How do you know? Here
are three ways to get to the root of a
problem without replacing good parts.