Check engine light is on but I can't scan any codes

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Here's someinfo if you cant retrieve codes.

Bill noted what I would do first, and that's go back to the old simple method to see if it spits codes.

Good luck.
 
What type of code scanner are you using? Is it one of those Actron units with the 2 switches on it? Also,did you plug in both the multi-terminal & single terminal connectors to the scan tool?

Plug the scanner in (both plugs).Make sure the switch is in the off (Standby) mode before you plug it in.Then,first turn the key on but don't start it.Now turn the scan tool in test mode and see if it gives you any codes.Turn the scan tool off,start your car and let it run for a few minutes.Now turn the scanner back on and your pcm should run a test.You'll know this because the engine will speed up for about 1 minute,then it'll slow and should flash a code/s.

Maybe the LED is burned out in your scanner?? Also,if the engine speeds up during the Key On Engine Running (KOER) test,then I highly doubt your scan tool is faulty...except the dumb LED.Try the Test Light method if none of that works for you.
 
Sometimes generic scanners don't want to retreive codes easily. I'd try and manually get codes by jumpering pin 4 and 7 on the DLC. By doing that you groud the STO and can read codes by the # of times the CEL flashes.

Your scantool should power up when you plug it into the dlc. The DLC grounds the scanner (ubless you have something like a NGS that has an external ground).
 
MustangLX-5.0 said:
What type of code scanner are you using? Is it one of those Actron units with the 2 switches on it? Also,did you plug in both the multi-terminal & single terminal connectors to the scan tool?

Plug the scanner in (both plugs).Make sure the switch is in the off (Standby) mode before you plug it in.Then,first turn the key on but don't start it.Now turn the scan tool in test mode and see if it gives you any codes.Turn the scan tool off,start your car and let it run for a few minutes.Now turn the scanner back on and your pcm should run a test.You'll know this because the engine will speed up for about 1 minute,then it'll slow and should flash a code/s.

Maybe the LED is burned out in your scanner?? Also,if the engine speeds up during the Key On Engine Running (KOER) test,then I highly doubt your scan tool is faulty...except the dumb LED.Try the Test Light method if none of that works for you.
I have two, an Actron and some othe cheap scanner that looks identical to the Actron. Both do the same exact thing, no flashing light. I tried several new 9 volt batteries, the LED does light while testing but I an not able to get anything during the test. I did follow yiour axact steps with the same results.
 
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.

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EDIT:
If that checks good, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector. You should see less than 1.5 ohms. Measure the resistance between the MIL computer self test connector (tan wire) and pin 17 on the computer main connector. You should see less than 1.5 ohms.


Diagram courtesy of Tmoss & Stang&2birds

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See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine

The following is a view from the computer side of the computer connector.
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