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5.0L (1979-1995) MustangTechnical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.
The 89 model should have a black/lt blue wire and a tan wire.These wires run between the ignition switch and cel
bulb and the self test connector (where a scanner plugs in to run codes) and pin 17 at the ecm.If you ran codes by using a jumper wire and the cel,because you don't own a scanner,and the cel failed to come on,a test light can be connected between the positive battery post and the STO terminal at the self test connector,so you can still run the code tests.The test light will flash the codes out just like the cel will.The following diagrams should help.
Last edited by wbrockstar; 08-25-2018 at 11:41 PM.
If you wanna use the jumper wire method instead of using a scanner,this is how its done.
*1* Make sure the ac is off
The shifter is in park/neutral (Auto)
The shifter is in neutral (T5)
The clutch pedal is down
The engine is at operating temp
*2* Connect a test light between the STO terminal (at the self test connector) and the
positive battery post.
*3* Connect a short jumper wire between the STI terminal and the Signal Return terminal (at the self test connector)
*4* Turn the key on/engine off and the test light will begin flashing codes out through the test light.
Last edited by wbrockstar; 08-26-2018 at 02:01 PM.
08-25-2018, 10:09 PM
