How to Read Codes From Your Check Engine Light (For Older Cars)

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Introduction: How to Read Codes From Your Check Engine Light (For Older Cars)

About: I've worked for Instructables off and on since 2006 building and documenting just about everything I enjoy doing. I am now the Creative Programs founder and manager for Autodesk and just finished building out…
You can pay a mechanic a bunch of money to read your car's error codes when your check engine light comes on, or you can grab a paper clip and read the codes yourself.

After 1996 all cars were made to hook up to an external error code reader. Before 1996 however, cars reported their errors from the computer themselves via a flashing code from the check engine light.

The dreaded check engine light comes on while you are driving only to signify that there is a problem. The specific error or failing part could be one of many different things that the computer senses for. You can bridge a set of wires in your car and send the cars computer into its error reporting mode so that you can find out whats wrong with your car.

Again, this instructable is only useful for people who have cars that report engine trouble via a flashing check engine light. This should be true for many cars made before 1996.

Here is a short video explaining the code deciphering process. For the full instructions check out the following steps.


Step 1: Find Your Vehicle's Diagnostic Plug

The first step is to find your vehicles diagnostic plug. The one in my car was a small blue plug that was bundled together with another factory plug beneath my glove box on the passenger's side of the car.

Just stick your head up under the dashboard on the passenger side and look around for a plug that isn't connected to anything.

If you don't have a Honda Accord then do a search online for where your plug is located and you will probably find some good leads.

Pull the diagnostic plug out from the plastic housing that is bundling it to the other set of wires under there (I think the second set of wires down there are sensors for the ABS brakes or the airbags).

Step 2: Bridge the Wires

Get a paper clip or a piece of wire with the ends stripped off. Stick one end of the wire or paper clip in one of the holes in the plug and stick the other end in the other. Make sure that it's making contact with the wires buy pushing it pretty far down into the holes.

Step 3: Watch the Flashing Light and Decipher the Code

With the wire in place, put the key in the ignition and put the car into the "run" position. That's two clicks for Honda users.

Wait a second and keep your eye on the check engine light. You should see it start to light up in a series of flashes.

The light is blinking in a simple code of long and short. Long blinks mean "10" and short blinks mean "1".

My light was blinking once for a long time, and then twice for a short time. 10, 1 and 1 is error code 12. Code 12 indicates a problem with my EGR system. This is the system that sends some of the engine's exhaust into the cylinder to cool the combustion process and keep temps in the cylinders down. Having a broken EGR is relatively common on a high mileage car (I have 180,000 miles on mine) and it's a pretty easy fix. I was worried that I might have to pull over to the side of the road when I saw the light or get it to a mechanic ASAP, but now I know that it's not life threatening to the car and that it's OK if I get it looked at the next time I am at my mechanic.

You can find a list of error codes for the make and model of your car online by doing a simple search. The ones for Honda are included below.

Honda Check Engine Light Error Codes

0 ECU
1 Oxygen Sensor
3 Map Sensor
5 Map Sensor
6 Crank Angle
7 Throttle Angle
8 TDC Position
9 No. 1 Cylinder Position
10 Intake Air Temperature
12 Exhaust Gas Reiculation (EGR) System
13 Atmospheric Pressure
14 Electronic Air Control
15 Ignition Output Signal
16 Fuel Injector
17 Vehicle Speed Sensor
20 Electronic Load Detector
22 Vtec System Malfunction
23 Knock Sensor
41 o2 Sensor
43 Fuel Supply System
45 System Too Rich or Too Lean
48 Primary Heated o2 Sensor
54 Crankshaft Speed Fluctuation Sensor
61 Primary o2 Sensor Circuit
63 Secondary o2 Sensor Circuit
67 Catalyst Sytem
70 Automatic Transaxle
71-74 Random Misfire
80 Exhaust Gas Recirculation
86 Engine Coolant Temperature Circuit
90 Evaporative Emission Control System Leak Detected
91 Fuel Tank Pressure Circuit
92 Evaporative Emission Control System Insufficient

1 Person Made This Project!

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44 Comments

0
scrappsesco13
scrappsesco13

Question 6 months ago

I have a 91 lincoln town car 4.6 liter. Recently the check engine light turn on i tried to decipher the codesbut after so many different ways i was told i still haven't been successful i did the paper clip bypass and the check engine light flashed 8. 5 second flashes can someone please help me with what the flashes mean outs highly appreciated

0
DanielH579
DanielH579

Question 3 years ago

My engine light came on while I was driving in my 1990 Honda Accord LX, so I pulled over and I listened to see if I could hear a new odd noise, I didn't. So I turned offrom my car then I started it back up and the engine light is now off. I found this site on how to scan the car. I did and my engine light just stayed on while I had the Bobby pin in, no flashes. What does this mean? My engine light hasn't come on ever sinceand that was a few days ago.

0
suziexsparkles
suziexsparkles

Answer 7 months ago

Because when you put the paperclip in to get the diagnoses it should do a series of short faint blinks and long ones which is your code then turn your car off then on again it removes the light on some vehicles for about 50miles or so then comes back on until you fix the problem. However, some vehicles engine light may come on just as a reminder to maintenance the car without there actually being anything wrong with it in which case you can get it reset at an auto store that does that sort of thing. But I would check all your fuses and then your ground wires, they're attached to every major component that makes the car run but if corroded or knocked off can cause wonky readings and stuff.

0
quietjean
quietjean

Question 9 months ago on Step 3

What does it mean if your engine light just continuously flashes?

0
suziexsparkles
suziexsparkles

Answer 7 months ago

Are you sure it's not just giving you a code? Make sure your diagnostic wires aren't touching. It would be behind your passenger glove box and make sure the brown and green wires aren't touching, if they're cut like mine were.
Youll know if it's a code bc there will be long blinks and short ones. Long blinks = 10 short ones are single numbers under 10

0
LeonieL6
LeonieL6

Question 1 year ago

Hi we have a Honda CR-V V-Tec 2003 model. The car started feeling sluggish at a few points whilst driving, thus being on a flat, down hill or up hill. The engine light has come on permanently. How can we do a diagnostic test? Someone PLEASE help as need the car for work & worried it's going to cost a fortune to repair

0
CRicky1
CRicky1

Question 1 year ago on Introduction

I have a 1994 Honda Accord with the SRS light on. At first it was intermittent, now on continuously. I've called around and checked the web on how to diagnose this light, but only find check engine light diagnosis, any help in enlightening me on how to figure it out?

0
ashleylkania
ashleylkania

Tip 2 years ago on Introduction

Wanted to add that for Chrysler/Dodge/Jeep vehicles you can accomplish this by turning the key on, off, on, off, on and leave in the on position. The light will begin to flash. Each blink is one count (so 4 blinks, pause, 5 blinks, is code 45). It will give as many codes as their are errors, then it will blink 55 at the end so you know you've read them all.

0
Shorty467
Shorty467

Reply 1 year ago

So I have a 94 Jeep Grand Cherokee 4.0 s6 4x4 and when I did the self diagnostic my check engine light blinked 3 times paused blinked 4 times paused blinked 5 times paused and blinked 5 times again what does this mean?

0
esdash
esdash

4 years ago

Was struggling with (the un-installation for short wiring and the re-installation of) this blue diagnostic clip until I've found this article (couldn't really crawled under to do it given the limtation in space, my car was parked along the through street's curbside). At least I get a clue about what's going on with the car prior to taking it to Autozone for free scan and some shops for price quotes. Thank you so much :)

0
esdash
esdash

4 years ago

Was struggling with (the un-installation for short wiring and the re-installation of) this blue diagnostic clip until I've found this article (couldn't really crawled under to do it given the limtation in space, my car was parked along the through street's curbside). At least I get a clue about what's going on with the car prior to taking it to Autozone for free scan and some shops for price quotes. Thank you so much :)

0
iplayguitars
iplayguitars

6 years ago on Step 3

Nice article! It is a pain if the check engine light comes and you are short on cash or a code reader! If you are near one of the major chains they can usually provide you with a printout of what the OBD reading says on your vehicle. It might not work for older vehicles but people who own newer models (mid 1980s and later) should visit this site: http://www.checkenginefree.com At this site you will be able to see auto parts stores near to you that offer free check engine light readings! Check it out!

0
MelissaL3
MelissaL3

6 years ago on Introduction

I have a 2003 kia Sedona with bad cat on bank 2 its a v6 front wheel drive so is it the front or back

0
jacob.bellinger.902

I have a 1986 Honda Accord lxi, The pgm-fi light is coming on periodically. I checked the code from under the driver seat, and it is a #17. The Vehicle speed sensor. My problem is finding out where on the car that part is located. It still runs fine most of the time. I just want to replace it because I have to smog the car soon. And this way I'll get out in front of the problem.

0
jacob.bellinger.902

I have a 1986 Honda Accord lxi, The pgm-fi light is coming on periodically. I checked the code from under the driver seat, and it is a #17. The Vehicle speed sensor. My problem is finding out where on the car that part is located. It still runs fine most of the time. I just want to replace it because I have to smog the car soon. And this way I'll get out in front of the problem.

0
kwagner12
kwagner12

7 years ago on Introduction

I used the paper clip trick myself. I was skeptical at first, however I got a good solid read. My issue is... The code I am getting is not in my book. 4 short pause 4 quick. I have a 93 Honda accord with 370k mi. I think I have a burnt valve (amongst so many other things.) So perhaps is it reading manifold pressure? Anyone with any suggestions? So thank you for the paper clip trick!! I couldn't get a jumper wire from the guys down at autozone! They said that they dont carry nor does anyone make jumper wires for vehiles older than 1996. One of the guys there told me something simular to do, however, it did not work. Your explanation as well as the idiot proof diagram and video makes it impossible to not get it right! THANKYOU!!!

0
toolguybuddy
toolguybuddy

7 years ago

I've been wondering how to do this and shakii take it to autozone if it has the obd2

0
shakii
shakii

7 years ago on Step 3

hy how can i read the codes of all new cars can u plz tell me

0
SPITFIRE226
SPITFIRE226

9 years ago on Introduction

Auto Zone can ONLY do '96 and newer. I have a '92 Buick LaSabre and can not find anyone with a machine to diagnose the problem