|Note: Here is the title page for the source document. It is believed that there is no copywrited material in this document, and thus was open to transcription to HTML. The GM restricted appendices have not been transcribed into this HTML document. The address for Dr. Smith is no longer current.|
It is the goal of this document to provide a comprehensive
listing of the Assembly Line Data Link
This document is ordered by year, engine displacement, fuel system, and producing division.
Thus, a 1984 Chevrolet 5.7 litre V8 engine would be referenced by: 1984 5.7 Litre TBI Chevrolet.
In the case where there are two different data streams
for a given engine, a letter classification will be added to
|Thus, for the purposes of this document, if the connector has twelve possible connections, it is numbered counter-clockwise starting from the “upper-right” corner.|
Temperature Sensor conversions
Load and TPS Conversion equations
Varying ALDL modes on vehicles
Year Disp Fuel
Year Disp Fuel
Closed Loop Carburetor Control
| If “N” is the number on the data line, then the corresponding
percent duty cycle can be calculated by dividing N by 2.56. For example:
|NTRPMX, the engine rpm variable has a 25 RPM per bit resolution.
Thus, when the NTRPMX is 20, the engine is operating at 500 RPM.
|FILTMPH is the actual miles per hour of the vehicle.
|The tables to convert ADTEMP and ADCOOL can be found below. For the Chevrolet and Buick multiport fuel injection (MFI) systems, the conversion is linear, subsequently only the equation is given. Load, LV8, and TPS information are also listed below. Any engine that is an exception to these rules will contain appropriate conversion information.|
|Chevrolet and Buick MFI:
If N is the value returned by the data stream in ADTEMP ( or ADCOOL),
then the temperature in degrees Celcius is:
|Degrees Farenheight =
|If LV8 is the load variable in counts, then:
|Every attempt has been made to define the abbreviations that are used in this document. It is, however, possible that some abbreviations are used without being defined. The following is an expansion of several comon abbreviations:|
| There are three classes of vehicles that have been produced by
GM since 1982.
[as of 1/86 - drb]
The first set of vehicles are those whose data streams are controlled
by placing a resistive value from pin B of the ALDL connector to pin A
of the ALDL connector. The vehicles, called resistive control (RC)
represent the largest portion of GM vehicles produced to date. 
These vehicles have the following modes:
The latter mode is also called shorted mode. These modes instruct
the Electronic Computer Module (ECM) about what functions perform and what
data to ship.
| The second class of vehicles are those that are controled by
shorting pin B to pin A. This class of vehicles is controlled by
the amount of time pin B is shorted to pin A and is called Pulse Width
Modulated (PWM) vehicles. To control the modulation, the cehicle
sets up a 0.500 second time frame during which it calculates the ground
time. The following list shows the relationship of the ground time
to the mode chosen.
|There are PWM vehicles that have times that do not correspond to these times (e.g., some Cadillac vehicles). Timings for various modes are presented wherever these timings are in conflict with the correct data.|
|The third class of vehicles is called GM30. The description of these vehicles can be found in the GM document XDE-5024 (see appendix d). [Not included in this HTML.]|