Beginner's Guide: Checking the Engine Trouble Codes

Pictures and Guide by Joshua Langevin

Two Digit Code List Three Digit Code List Checking the Codes

This is a step by step guide to checking the engine trouble codes in your SHO. Remember that just because your CEL (Check Engine Light) isn't on does not mean that there are no codes stored by your computer. If you are having troubles with your SHO, this is the first place you want to go.

There are three tests, KOEO (Key On Engine Off), KOER (Key On Engine Running), and the Cylinder Balance Test.

KOEO

1. Make sure the engine is warmed up to normal temperature. The car should be in neutral, parking brake set. Shut the heater/AC off. Locate these two plugs under the hood, on the passenger side of the firewall. They have covers over them that you must remove.

2. Now use a jumper wire and connect the upper-right pin on the black plug with the large pin in the grey plug, like so. A paperclip seems to be a popular choice. :)

For a better look at where this jumper wire goes, look at this diagram. Connect the jumper to the red dot on the connectors.

3. Now jump into the car, and make sure you have a pad and pencil ready to jot down the codes. Now turn the key to "On", but do not start the car. You will see the CEL blink and hear the whirr of the cooling fan being tested as well as the fuel pump. Then the codes will start being displayed.

The codes are displayed by the CEL in flashes separated by pauses. If you have a Gen I (89-91) there will be two sets of flashes, if you have a Gen II (92-95) there will be three sets. As an example, a code of 256 would look like this: *flash*flash* PAUSE *flash*flash*flash*flash*flash* PAUSE *flash*flash*flash*flash*flash*flash*.

The common code 114 would look something like this:

(This animation will repeat every few seconds.)

It can be a little confusing at first, but the car will display the codes twice. Then it will flash once, and then move on to the stored codes. These are the codes that have been stored by the computer but may or may not have found when testing.

KOER (Key On Engine Running)

Now, start the engine. The CEL will blink 3 times. Watch the RPM guage carefully, and when you see the RPMs rising (the computer is advancing the timing) then follow these steps: (this is so the computer know these things are working)

1. Turn the steering wheel 1/2 turn to the right and then to the left.
2. Step on the brake
3. If your car is an ATX, switch the overdrive off, then back on.

In a moment the RPMs will go back down and the check engine light will flash once. Now step on the gas for just a second (at least 1/4 way down). Now the codes will be displayed.

Clearing the Engine Codes

Generally, the best way to clear your codes is to disconnect your battery for at least 10 minutes.

Cylinder Balance Test

This is to make sure that all of your cylinders are working right. After you have run the above test, press the gas pedal down again at least 1/2 way, just for a second. The RPM guage will move and the engine will start running a little rough. This is because your computer shut one of the cylinders off. It will do this 5 more times, once for each cylinder. Then it will display the codes.

Three Digit EEC Codes (92-95 SHO)

Two Digit EEC Codes (89-91 SHO)

Cyinder Balance Codes

10    Problem with cylinder 1
20    Problem with cylinder 2
30    Problem with cylinder 3
40    Problem with cylinder 4
50    Problem with cylinder 5
60    Problem with cylinder 6
9      No Problems