84CUCV
3/4 ton status
its a 87 with a bbc. i was not there for this, but he said he would plug the scaner in and nothing would happen. the scaner is good. computer? any ideas?
thanks
thanks
CK5
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do the tbi computers go bad
- Thread starter 84CUCV
- Start date
Thunder
3/4 ton status
So what is the problem with the truck? ????
If the scaner does not work I would try resetting the ECM. Disconnect the - batt cable for a few minutes. Reconnect. Fire up the engine, drive, then check codes.
If the scaner does not work I would try resetting the ECM. Disconnect the - batt cable for a few minutes. Reconnect. Fire up the engine, drive, then check codes.
84CUCV
3/4 ton status
truck will not start. ecm does not seam to do a thing. put the scaner on my 87. no good. put it on my 91 works fine. its like the ecm is dead??? the scaner does nothing at all
84CUCV
3/4 ton status
i did what you said
More info might help. Is this a scanner, or just a code reader?
Scanner doesn't work on your truck either, but yours runs?
Does the check engine light come on in the "dead" truck? Are the fuses good? Are they getting power?
ECM's can and do go bad, but it is quite uncommon that they are the real problem. More often than not, they aren't the issue, and people just waste money buying rebuilt ones that aren't that good anyways.
My truck wouldn't start after getting hot. Followed the GM troubleshooting guide, repeated the tests multiple times, tested things on my own, only thing left seemed to be the ECM, flow charts confirmed it, as did deductive reasoning. Got my hands on a rebuilt ECM, swapped it, truck started every time. Bought new injectors, threw them in, then on a whim put the "bad" ECM's (had two that did the same thing) in the truck, and voila, they worked again. It was the injectors that were the real problem. Still running on one of the "bad" ECM's.
Scanner doesn't work on your truck either, but yours runs?
Does the check engine light come on in the "dead" truck? Are the fuses good? Are they getting power?
ECM's can and do go bad, but it is quite uncommon that they are the real problem. More often than not, they aren't the issue, and people just waste money buying rebuilt ones that aren't that good anyways.
My truck wouldn't start after getting hot. Followed the GM troubleshooting guide, repeated the tests multiple times, tested things on my own, only thing left seemed to be the ECM, flow charts confirmed it, as did deductive reasoning. Got my hands on a rebuilt ECM, swapped it, truck started every time. Bought new injectors, threw them in, then on a whim put the "bad" ECM's (had two that did the same thing) in the truck, and voila, they worked again. It was the injectors that were the real problem. Still running on one of the "bad" ECM's.
Thunder
3/4 ton status
As Dorian said check the fuses. There are 2 on the fuse pannel. ECM 1 and ECM2 or they may be marked ECM A&B. Also check for bad grounds. Check the ground strap between the engine block and firewall. Check the connections at the ECM. Take a look at the wires that feed the injectors sometimes the insulation gets wore out or pinched and shorts to ground.
84CUCV
3/4 ton status
fuses are good. i was wrong, it just reads codes. i will check for power at the fuses. didnt think of that. will check the gounds. will check the wires.
let you know how it goes. thanks guys
let you know how it goes. thanks guys
So does the check engine light come on when it's supposed to? If not, then the bulb is the likely problem.
No reason to waste time hunting down grounds, power, etc., if that light doesn't work when it's supposed to, you need to figure out why first.
No reason to waste time hunting down grounds, power, etc., if that light doesn't work when it's supposed to, you need to figure out why first.
Also confirm the pinout of the ALDL connector -- I've seen the data wire positioned in a few different spots on different TBI rigs...
84CUCV
3/4 ton status
ALDL? rain stopped us today thanks
loafer
1/2 ton status
84CUCV said:
That's the thingy you plug your scan tool into; Assembly Line Data Link.
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84CUCV
3/4 ton status
got it thanks
84CUCV
3/4 ton status
still no luck
84CUCV
3/4 ton status
after a lot of choice words. its running good. i dont understand tho. a friend got a puter of some scrap guy he knows. put it in, didnt think anything would happen. started right up. i would like to understand this. how do i test the old one. also, i think everyone should have a bbc. all stock too. wonder what a built one is like.
thanks for the help
thanks for the help
84CUCV
3/4 ton status
anyone
All sorts of things can go wrong with them. Common is the injector drivers.
AFAIK the only way to properly test one of these things is a custom made test bench. Probably need things like a multimeter, oscilloscope, and so on as well. USUALLY for the cost, it wouldn't be worth getting the tools to test them correctly.
Easiest test most can do is find someone else with the same vehicle, and swap the ECM into it and see what happens. If the problem is replicated exactly in the other vehicle, it's the ECM. If it isn't, something else is the real cause (like bad injectors in my post above) and a new/different ECM may only be a band-aid, until it too is (potentially) overwhelmed by the problem.
AFAIK the only way to properly test one of these things is a custom made test bench. Probably need things like a multimeter, oscilloscope, and so on as well. USUALLY for the cost, it wouldn't be worth getting the tools to test them correctly.
Easiest test most can do is find someone else with the same vehicle, and swap the ECM into it and see what happens. If the problem is replicated exactly in the other vehicle, it's the ECM. If it isn't, something else is the real cause (like bad injectors in my post above) and a new/different ECM may only be a band-aid, until it too is (potentially) overwhelmed by the problem.
84CUCV
3/4 ton status
OK i see. i was thinking take it apart. see what burnt up and replace it. guess not
thanks
thanks
Well, it can't hurt to do that...there are plenty of components in there that COULD go bad and leave a visual clue, (charred component for instance) and if it doesn't work right, you can't make it worse. They are very simple to disassemble and peek at, but I can't tell just by looking at one which part does what.
84CUCV
3/4 ton status
took it apart. everything looks good. beats me
