Pulling PCM (Computer) Error Codes w/o A Reader

Many occasional mechanics don't have a reliable engine error code reader on hand to pull the codes from today's modern engines and diagnose problems. If you are more than just an "annual mechanic" (doing repairs maybe once a year), you should invest a few dollars in an engine error code reader. Find out more here.

You can pull the codes without a reader, however, but it's not always simple and many find themselves doing it several times to get the codes written down accurately. Here is a recommended procedure that works on most of today's vehicles and will minimize your mistakes when recording the codes manually.

First, make sure your vehicle has batteyr power so that it can power up - not necessarily start, just be able to turn on all dash lights when the keyswitch is in the "on" position.

Next, prepare your recording device. If you have a camcorder or digital camera capable of taking video for at least 30 seconds, use that. Otherwise, your mobile phone will likely work as well. The idea is to "record" the engine light blips you're about to receive so that you can play them back easily and fast-forward/rewind as needed when decoding them.

Using the camera, set it to record and point it at the engine error light on the dashboard. Turn the key quickly to the on, then off, then on, then off, then on, then off, then on position in five seconds or less.

ON-OFF-ON-OFF-ON-OFF-ON

Now wait. The engine light will begin flashing the error codes in two-digit flashes. So the number 31 would be "flash-flash-flash, pause, flash." Record the whole event if you can as it's rare for only one code to be set. There are usually several.

If you can't record it, then have a dictaphone, voice recorder, your phone's voice mail called, or a pen and paper handy so you can quickly record them as they come. Don't try to decode as you record, as this will just slow you down and cause mistakes.

Once you have the codes, if you need to go back, you can repeat the process to display them again, but it will only do so from beginning to end and so you'll have to sit through the entire thing repeatedly until you have them all down.

Nowt hat you have the codes, check what system your vehicle uses (likely OBD-2) and decode the numbers given to you per your vehicle's owner's manual and/or the Internet.

Once you've fixed the problem, try this procedure to quickly reset the computer and remove the current codes.