Can't Pull Codes!!

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Use the diagram above and check the resistance of the wires that run to the self test connector. If they are all less than 1 ohm, either the computer is bad, you have some bad connections on the black/white signal return wire, your test proceedure was incorrect, or the computer is bad.

Check the resistance of the black/white wire to battery ground. If it is less than 1 ohm, it is good. If it is more than 1 ohm, the black/white wire has bad connections or a broken wire. Always take resistance measurements with the circuit powered off.

Some help on the test proceedure...
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.

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/article...c-iv_codes.html

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

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.

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

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart .

Hoffman said:

Just bought an 89 LX 5.0, The check engine light stays on all the time..
I Jumped the Self Test Input and SIG RTN terminals, and hooked up my test light, but nothing. The Check Engine light wont flast, and the voltmeter method won't work. And yes I did hook up the voltmeter to the STO output to positive battery terminal. Any Ideas?

Click to expand...

Take a look at your self-test connector. Hold it so the row of 2 ports are on top and the row of 4 are on the bottom. Try running a wire from the port on the upper right directly to battery negative. Now do the same thing with the self-test input (the one that's hanging off by itself right next to the self-test connector) - jump it to battery negative. Put your car in nuetral, turn the key on (don't start it), wait a few seconds and see if your check engine light starts flashing.

If this works, you have a blown ground circuit in your computer or the computer ground is bad. You can check to make sure the 2 black wires going right to the battery negative terminal (wired in to the connector along with the thick black wire) are clean, but it's usually the circuit that goes.

Let me know if that works.