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Engine diagnostics with no ALDL Connector?

Guest Ansis42

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Guest Ansis42

Hey Everyone,

Recently, the 'Engine' light on my 1980 Buick Lesabre has come on. It only comes on when the key is turned on. It does not stay on while the engine is running. I have been trying to figure out how to extract the engine problem codes. I have a Haynes manual that discusses how to use the ALDL Connector to extract the codes. After much searching, I am not able to find this ALDL Connector. I did some research online, and came across a 1980 El Camino driver, who noted that his car does not have an ALDL Connector! So maybe this is something that was not available for older GM cars? If someone has done this before, I would greatly appreciate the steps to extract my engine problem codes! Thank you very much.

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If the light is not on when the engine is running then you do not have a sensor problem. The light most likely comes on when the key is turned on because that is a test to make sure the light actually works. Do you have an owners manual in the glove box? That would probably explain this.

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The "Assembly Line Diagnostic Link" (aka "ALDL") was NOT an option, but a normal part of the "computerized" vehicle's computer system. I don't believe they appeared until the middle 1980s when full ECMs were what controlled the engine's activities . . . rather than "stand alone" items as carburetors and ignition distributors. Seems like, at least on Chevrolets, that it was the 1981 model year, possibly 1980 in California, that there was even an ECM . . . period.

Therefore, with NO on-board computer system, NO place for an ALDL, either. IF there was an ALDL, I'm not sure what "community interface" it would be hooked to! If you found the picture of whatit was on the El Camino, you'd find the same thing under the lower edge of your instrument panel on your Buick. They ALL looked the same and you shorted the same terminals to get the "Check Engine" light to flash the diagnostic codes (in the absence of a scanner which would present them in a digital readout).

In 1980, there might have been some particular states or regions of the country which had to have a computerized carburetor or similar, which would have a computer to run it, from input from various sensors in the engine and exhaust system. Rather than build an instrument cluster specific to those regions, they'd build ONE that would work everywhere and then use the "Engine" light in the same manner the "GEN" light would always illuminate while the vehicle is being cranked, or similar. In the particular regions, the "Engine" light would illuminate when the computer detected values from any sensor which were considered to be "out of normal range".

It's been a while since I've thought about when all of those things began . . . There were LOTS of things we got by the middle 1980s, but FEW in the early part of that decade . . . other than catalytic converters, AIR pump systems, evaporative emissions systems, retarded ignition timing, and leaner fuel mixtures . Best as I can recollect.

I DO concur that if the light is not on while the vehicle's engine is running, there should not be a problem. What happens during the "START" cycle is unique to that activity.

Just some thoughts,


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Guest pfloro

My understanding is that beginning with the 1981 model year, GM began using it's CCC (Computer Command Control) engine management system on all of it's domestically sold cars. I don't believe that GM carburetor equipped engines used CCC prior to 1981. However, as NTX5467 stated, perhaps CA and/or other states required CCC in 1980. GM used computer controlled throttle body fuel injection on at least the 1980 Eldorado (digital EFI).

Remove the air cleaner from your 1980 Buick Lesabre. If there is a 2 wire electrical connector on the top front passenger side corner of the carburetor, then this car has CCC. It will also have a 3 wire connector on the front driver side. BTW, the 'CHECK ENGINE' light should have an amber lens with 'CHECK ENGINE' printed behind it...

It's possible that the ALDL connector was either cut out or unscrewed & tucked under the steering column trim cover... You might want to remove this plastic cover take a look. If you find the ALDL connector, the 'A' & 'B' terminals (right side) are simply jumped with a bent paper clip to 'enter diagnostic mode'. Turn the ignition ON without starting the car, jump the A & B terminals, and watch the Check Engine light. The only code you should 'see' is a 12 (no distributor reference pulse). The light will illuminate for a slightly longer time for each 'tens' position followed by a quicker flash for each 'ones' position. Each code will be 'flashed out' 3 times. Then the sequence will repeat. For example, a '12' = one long flash followed by two shorter flashes / a '34' = three long flashes followed by four shorter flashes. It's like riding a bicycle once you see it happen for the first time.

The first generation GM CCC system was known as OBD I (on board diagnostics one). The Diagnostic Trouble Codes are well documented on the Internet.

OBD-1 Diagnostic Trouble Codes

I hope this information is helpful.


Edited by pfloro (see edit history)
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