How to test for 'bad' computer ? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-20-2003, 01:29 PM   #1
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Default How to test for 'bad' computer ?

I'm new to the list......my dad has an '87 Bonneville that has recently started bucking like a wild horse. I'm in a different part of the country than he is, so I'm trying to help him diagnose things remotely. I've already suggested he check the fuel filter and MAF, but I was wondering if anyone knows of an easy procedure for checking to see if the computer is starting to go south ?

Thanks in advance.
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Old 07-20-2003, 01:34 PM   #2
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swap it for a sec with a junkyard computer of the sorts. btw, what was the last repair he did before it started
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Old 07-20-2003, 06:54 PM   #3
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Swapping with a junkyard computer is not an option. I was hoping there was a way to diagnose this, perhaps with some of the commonly available diagnostic software.

Last repair/maint. item was plugs & plug wires many months ago. His car has been running fine up until the last week or so.....
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Old 07-20-2003, 07:16 PM   #4
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Is he getting a Service Engine Soon or Check Engine light ? Could be a lot of things. Does it start as soon as he starts the car or a few minutes later ? Computers rarely "start to go south", they either are good or bad. MAFs rarely fail. Fuel system problems are generally worse under load (when driving) than at idle.

These computer cars really need proper diagnosis.
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Old 07-20-2003, 08:52 PM   #5
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has the ECM been reset to try to fix the problem? might want to try that, so the computer will have a fresh start. do remember to jot down all of your desired information thiough, along with any other things a disconnected battery might cause. also, look for any unplugged vacuum lines. those are a pain. i dont know if a vacuum line would throw a code too. btw, does his SES light work?
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Old 07-29-2003, 06:36 PM   #6
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Well, I helped my dad make some progress on this problem.....the Check Engine light was not lighting up, but I did talk him through jumpering the 'A' and 'B' pins on the ALDL connector....error code 33 was in memory, and I understand this does happen on these cars (code 33 dumped into memory, but check engine light isn't triggered). So, he went out and got a reman Borg-Warner MAF - the car ran crappier with the reman, so he put the original one back in.

I'm wondering if this suggests that the computer is on its way out. He doesn't have access to a scan tool or any diagnostics */w, so I'm not sure how much more troubleshooting he'll be able to do by himself.

Thanks in advance for any thoughts.
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Old 07-30-2003, 12:09 AM   #7
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Personally would crank up one of my OTC 2000s (around $25 on e-bay - make certain you get the right cartridge and adapter cable for your car) and see if the data stream coming off the ALDL connection makes sense. If so the ECM is probably good.

Error code in the flashes but with the SES light off means that it happened at some time in the past (history) but is not current. At least you know that since the response to jumpering happened, the computer is doing something right. Is really time for a proper scan tool like the OTC.
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Old 07-30-2003, 09:03 PM   #8
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I suggested my dad get a Cardone MAF and try that - he found a diff. local parts store that carries them - it worked. So either the Borg-Warner MAF he got the other day was a dud, or the car just didn't like it.

Thanks for everyone'* feedback....I suspect I'll be staying on the list for awhile....
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