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Year 1955 Manual Transmissions 75 Units
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Year 1964 327 ci / 300 HP 10,471 Units
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Year 1996 Coupe base Price $ 36,785
On Board Diagnostics
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.
Electronic Control Module Photo
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.
Recovering Trouble Codes
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.