|Remove the ALDL cover (in the unlikely event that there still
is one in the automobile...they usually were lost early in the
automobile's lifetime) and as you view the pins, you will find
the top row fully populated whereas not all are populated pin
on the bottom row.
|On the top row (as you view the connector from the cockpit),
the pin designators are F,E,D,C,B,A.
|Here is a typical 12 pin connector. (Some have more pins on
the lower row than this example). The pins you are interested
in are those two pins in the top, right hand portion of the connector,
designated pins "A" and "B". Pin "B"
is the diagnostic enable pin and pin "A" is ground.
By grounding pin "B", you enable the diagnostic readout
functionality of the ECM/PCM.
|To recover the codes, it is necessary that you short pins "A"
and "B" together using a small section of electrical
wire. Alternatively, you can cut up a paper clip and fashion it
into a shorting device. Regardless of your method, you will want
to utilize something that will reliably make contact with the
two pins but will not damage the connector or the pins. With the
ignition turned Off, short pins "A" and "B"
on the ALDL using your previously prepared pin shorting device.
Turn on the ignition but
Do Not Start the Automobile.
|Within a few seconds, your Check Engine light (early
C4s) or "SYS" light (later C4s) will flash a code of
12. There will be a single flash followed by two flashes and this
will repeat three times: Flash (pause) Flash Flash (long pause),
Flash (pause) Flash Flash (long pause), Flash (pause) Flash Flash
(long pause). Code 12 is a delimiter or marker code to show where
the error code string begins and ends.