Digital Tuning Check Engine Light Question (94 Cobra)

Discussion in '1994 - 1995 Specific Tech' started by webshot, Mar 19, 2012.

  1. I was wondering is it possible to have potential trouble codes in the car computer without the check engine light being on?

    Also which code scanner do you guys recommend?
    (This will be personal use, if you have links to the scanner that would be great)
  2. Yes, codes are usually stored. The scanner can not only check them but you can clear them as well. I have a small hand held I got at Pep Boys for like $29.
  3. So not all engine problems will trigger the check engine light? I was told by someone "if your check engine light is not on then there is no problems in the computer/engine". Something about that statement didnt sound right. But thanks VibrantRedGT, I plan on picking up on from Autozone. Didnt know if there were certain functions or features I should look for in a scanner.
  4. If the codes were never manually cleared they will stay stored and there won't be a check engine light on. You can get rid of a check engine light by disconnecting the battery for some time. If the problem only happened once then that code you disconnected the battery for should be stored. With the code scanner you can clear all the stored codes. The codes not cleared doesn't mean it's making your car run poorly. If you have Check Engine light on now that persists then you have a problem.
  5. Ok cool, thanks. Because I want to start asking some questions here about my engine issues. But it seems the first thing that is asked is "run the codes". But if my check engine light is not on and the codes have been cleared previously. Then there is no real need to run the codes again right?
  6. The code scanner I just ordered was the Innova 3145. I got it from Summit Racing and it was about $27 shipped. Its nice since it actually reads and displays the codes instead of trying to count how many times the CEL blinks.
  7. Pulling codes only takes a few minutes so, if there is an issue you want to see if the PCM has picked up on a sensor reading that fell out of spec. It's a valuable diagnostic tool every 94-95 mustang owner should own.
  8. Thanks Toyman, yes I am grabbing one this weekend.
  9. All autozone had was the ones with the blinking light. So I ordered the one Jdubz did from summit. Jdubz how is yours working for you?
  10. Mine worked very good. Very easy to use and its nice since it stores the codes on it until you run the test again. But since I got really impatient waiting for it to arrive, I actually got really good at counting the blinking CELs and got the same codes. But it is a must have if you are trying to diagnose a CEL, especially if you have a lot of codes.

  11. I got the same one. Mine came alarmingly fast too.. haha. Thanks for the input
  12. Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

    Dumping the computer diagnostic codes on 86-95 Mustangs

    Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

    Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

    Here's the way 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.

    Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

    Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
    Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.



    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.

    WARNING!!! 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. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

    Some 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 clutch (if present) is pressed to the floor, 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.