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Check Engine Error Codes

In one of the recent shows, Tom and Ray said you need a gadget to read the check engine error codes. On my 1990’s Toyota, I can read the check engine code by inserting a jumper in a connecter under the hood, then watching the “check engine” light blink. It blinks out the code sort of like morse code. If the code is 38 for example, it will blink 3 times, pause, then blink 8 times. No gadget needed.

I wonder, do newer Toyotas still have this feature, or does the home mechanic have to purchase a gadget now? Why design a car that needs a gadget to read the silly codes? The blinking method works fine and no gadget needed. Is there a reason for this?

The codes got a lot more complicated, you need the code reader now.

Older cars used OBD-1 diagnostics…Their usefulness was rather limited and the codes were not standardized. With the current OBD-2 system, the connector, tool and codes are standardized and far more detailed than the old system…If you own a laptop computer, you can by a USB to OBD-2 cable and diagnostics program for under $40 that will not only read the codes and clear them but will also provide a real-time monitor of the entire engine management system…

There are hundreds of codes in OBD-2 systems. Blinking read-outs are impractical. I suspect that cars could easily be made to display error codes in their own read-outs. My guess is that they don’t do this because the carmakers know that many people really shouldn’t be diagnosing and attempting repairs. Code readers are pretty cheap, but having to buy one is a small barrier that I suspect is put in place to reduce the number of unqualified people who attempt repairs.

The purpose of the system is to minimize pollution. I suspect that if the car told the owner “P0401 EGR Insufficient Flow,” many owners would simply replace the EGR valve instead of diagnosing the system properly. The OBD system won’t minimize pollution if people don’t use it correctly. So the small barrier to working on your own car keeps some unqualified people from working on things they shouldn’t.

“many owners would simply replace the EGR valve instead of diagnosing the system properly”

Many mediocre mechanics will do that too.

So, does anyone know what percentage of the time replacing the stated part actually does fix it? One percent, or 60% makes a big difference. I can see where some people will simply try the stated part, replacing it themselves, and for many parts at modest cost, rather than going through all the hassle, trying to find a competent and honest mechanic, which takes people a long time to accomplish. I got to the stage where, before I retired, I knew who would do a good and honest job, but that took years of hunting and tolerating lousy and incompetent service. Now, I go to the dealer in McAllen, everything fixed and fixed right the first time. I don’t yet need many repairs, that may change, I will post that separately.

plus, it’s easier to check the codes with the machine. By your car’s way of reading, and 2 other maker’s methods I’ve found, it’s different for each manufacturer.

You should find the diagnostic connector under your hood normally by the fender on the battery side. By just using your test light and a jumper wire, it will tell you what kind of problem you got.


  1. Make sure engine is fully warmed. If in doubt, run engine at 2000 rpm for 2 minutes.2. Turn ignition off and wait 10 seconds for system to shut off. Make sure A/C is off and transmission is in Park (automatic) or Neutral (manual).3. Hook up light and jumper (or a tester if you have one). Turn key to ON (do not start engine). Read the codes.

How to do it?

Example code 23: your test light should flash 2 long consecutive flashes followed by 3 short pulses.

Ford’s common codes for OBD1 (vehicles made before 1995)
taken from here:

BMW vehicles obd1 code retrieval

You can get the check engine light codes of BMW vehicles for models made before 1995 using the check engine light. All you need to are:

Turn ignition key to run with engine not running
Depress gas pedal 5 times in wide open throttle (WOT) position within 5 seconds
Read the flash codes in the dash using the code table below.

So, I can look up which vehicle I have and do their method of testing for OBD1, or I can find the diagnostic port and plug a little machine into it and get the codes. Will autozone loan you a test light and/or jumper wire to get the OBD1 codes? They usually read the OBD2 codes for free

You can still retrieve the basic codes by doing the ‘key dance’ on Chrysler vehicles. Turn the ignition on-off-on-off-on. (without starting the car) It has been possible to do this since the early days of OBD1.

As others have mentioned, to do in-depth troubleshooting, a scan tool is really needed.

As engines have gotten more complex so has the need for an advanced method of reading the error codes.

Many auto part stores will read the codes for free. Most modern engines will generate an error code in the format [P0123] While that will not mean much to you, if you come back here and post that error code, someone here may be able to tell you what the code means and what you should do.