Check Engine light ???

TrickFlowd · Apr 18, 2009

Check engine light turned on today, and comes on after every start. Car runs and idles perfect and drives just the way it did the day I bought it. Any idea on whats up with this light? Its prolly getting close to due for an oil change, that wouldn't have anything to do with it?

Black 93 Fox · Apr 18, 2009

Take it to auto zone they do a computer scan for free.

93tealstang · Apr 19, 2009

Any of the chain auto stores will put it on the scanner and pull codes for you. The device they use is only about 20 bucks or so and will come in handy for any future codes.

jrichker · Apr 19, 2009

How about doing it yourself for the cost of a paper clip?

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

TrickFlowd · May 12, 2009

My car is a 92 AOD, I tried the self test method...but it wouldn't throw a light. The car sometimes throws a check engine light...and other times I drive it, it doesn't come on at all. When I did the self test method, the fuel pump cycled twice...but no light. Also, the wire color on the single wire connector is yellow with a black stripe. Its in the same plastic connector cover as the big black plug for the tester. If that makes sense. I'm positive its the right connector. But not sure why its not throwing a light......

jrichker · May 12, 2009

TrickFlowd said:
My car is a 92 AOD, I tried the self test method...but it wouldn't throw a light. The car sometimes throws a check engine light...and other times I drive it, it doesn't come on at all. When I did the self test method, the fuel pump cycled twice...but no light. Also, the wire color on the single wire connector is yellow with a black stripe. Its in the same plastic connector cover as the big black plug for the tester. If that makes sense. I'm positive its the right connector. But not sure why its not throwing a light......

Start your own post and I will do my best to get you the correct answer to your problem. Hijacking or piggybacking on someone else's post just creates confusion. Thank you for your cooperation.

TrickFlowd · May 12, 2009

jrichker said:
Start your own post and I will do my best to get you the correct answer to your problem. Hijacking or piggybacking on someone else's post just creates confusion. Thank you for your cooperation.

This is my own post...I just haven't had the chance to look in to the problem with the diagrams and info you gave me weeks ago. Look at the top and you can see I was the one who started it. Sorry for the confusion.

jrichker · May 13, 2009

My mistake on the user name.

You must be looking at the wrong connector. I can't find a yellow wire with a black stripe on the computer wiring harness.

Diagram courtesy of Tmoss & Stang&2birds

TrickFlowd · May 13, 2009

Here is the plug I used to jump to the big plug. This little one wired gray plug is attached to the big black plug in some sort of holder, and its attached to the strut tower. Hope this helps...

View attachment 258139

Check Engine light ???

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