When the ominous “Check Engine” light comes on, it could be anything from a loose gas cap to an engine dangerously close to overheating — so it’s a good idea to get it checked out ASAP. Years ago, there wasn’t much of an option besides taking your car into the shop to get hooked up to their expensive diagnostic tool to tell you what’s going on.
These days with new technology, diagnostic scan tools have become affordable enough to add to your own DIY arsenal. The question then becomes: How do you use one?
Vehicles boast a complex series of sensor-powered, on-board “self-care” systems to keep them driving reliably for years. All of these are linked up to a central computer, the ECU, which takes data from sensors and switches, and translates the data into actions, whether that’s decreasing fuel consumption or keeping your brakes from locking up. When there is a fault, the check engine light comes on, the ECM stores a code pointing to the detected problem, and then it intuits the missing data needed to keep the vehicle going as smoothly as possible. The standardized OBD II (On Board Diagnostics) port is the result of a federal mandate ensuring all vehicles manufactured after 1996 are compatible with the same connector. The port is connected to the ECM so that when a scanner is hooked up correctly, it can pull a list of all trouble codes stored within, giving you a good starting point to solve the problem.
How to Scan
OBD II ports are generally located under the dash on the driver’s side. With the key out, plug in the male side of the scan tool. Some scanners get power from car batteries and some power from within, so follow instructions to get your diagnostic tool powered up. Once it’s on and connected, turn the key to the on position but don’t start the engine. Follow the instructions on the diagnostic tool screen to look up codes and where applicable, clear them. You cannot use a scanner to clear codes to pass an emissions test without the problem itself being fixed. To pass inspection, the car has to be driven long enough for the ECU to register no faults as opposed to simply cleared faults.
There are a wide variety of scanners on the market, from less expensive, straightforward code readers to models costing in the thousands with all kinds of special features and abilities. There are also apps available for download on smartphones, but you still have to buy the cable. They all plug in exactly the same, and they all provide on-screen directions for how to proceed.
Cracking the Code
Ultimately, even a simple code scanner will be enough for most at-home diagnostics. Know that you might get more than one trouble code and that they could be related or separate issues. With codes in hand, head to the internet. Type in the code along with your vehicle year and make, and see what pops up. Chances are it’s being discussed in a forum somewhere already, or you could always consult your local auto parts store for advice. Remember, the computer doesn’t know the difference between a bad sensor and the mechanism it governs, so a code leading you to a fault with the O2 sensor could actually have a number of base causes, and you’ll need to perform further tests to get to the bottom of it.
For more information on using a diagnostic tool, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photos courtesy of Bosch Automotive Service Solutions and Blair Lampe.