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94 buick lesabre custom diagnostic cannot connect to or read ecu/intermittent stalling/rough running

I have a 94 buick lesabre custom that is stalling intermittently and runs rough intermittently. We have had it for diagnostics and it could not read the codes. We changed the computer and it still can’t read the codes. The diagnostic tool says it cannot connect when it is plugged in or it displays white flecks like snow flakes on the tool screen. It is an OBDII. The pin structure of the data connector port is two pins top row and bottom row two pins some blanks and one pin. We don’t know how to fix it with no diagnostic codes and we don’t know what to do to get the codes because we have changed the computer. Has anyone ever seen this before? Any suggestions?

GM started phasing in OBDII in the late 94’s and early 95’s. So you may have a non-compliant OBDII system.

Know anybody with a GM TECH II scanner?


It’s quite possible for this to happen for early 90’s cars. That’s around the transition time period for OBDII. Newers code scanners could be expected to have difficulties. You’re probably going to have to ask someone at a Buick dealership for help on this. If you have the Buick service manual for this car, that would probablly tell you what’s required to read the codes. There may in fact be a way to read them without any scanner, if they put in a “blink” option, where a dashboard light is used to blink out the codes in a sort of morse-code fashion. But I’m assuming you don’t have the service manual. So off to Buick. They have the manual, and can help you out on this I expect.

This was a tough time for scanners. It may really be odb1. That alone will cause fits for an odb11 scanner. The blink scan that @georgesanjose suggests is the best first test. Usually you turn the key on and off in a special way, then the engine light blinks. Your mileage may vary.

94 buick Lesabre with the 3.8 and the 16 pin dlc does in fact have obd2. Have you checked the fuse? Otherwise with a car that old, perhaps your looking at chasing wires at this point.

Have you tried going about the codes this way?
This appears to be the connector that you have.

paper clip scan tool time and count the flashes

That diagram link of the DLC looks a lot like the one in my 94 Suburban. And yes my scan tool is a paper clip (with a few bends removed) connected between the B and A terminals. Turn the key part way (but don’t start) and wait for the Service Engine Soon or Check Engine Light ‘hand shake’ code which in my case is 12 represented by one flash followed by a pause and then two flashes in rapid succession. This repeats three times. Stored codes will then similarly appear eg 32 is three flashes pause two flashes. Each code repeats three times (in my truck) so you have to wait to see if there are more than one. Once all codes have been found you will get the ‘good-bye’ handshake 12 which will also repeat three times.

I had a reading problem with our 95 Olds too. It was a transition period and the only ones that can read the code are the ones with the advanced tech system such as the dealer. You need a different mechanic with the advanced equipment. I don’t believe you can read these with the paper clip anymore if it is OBD2.