GM Computers

[BOB URZ]

My 96 S10 seems to have some issues when its cold and i am suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and checking
solder joints or such. But, i don't not have a spare and do not want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line successfully?
Any pictures internally if you did? Any tips? This is a OBDII unit.

BOB



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[David]

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.

The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

There is also a good chance the grounds (any of about 6 or 7) could be bad.

The GM computer is a very low failure item, look to it last for your
problem.

David

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message
news:3F804DED.88A00550@inetnebr.com...

My 96 S10 seems to have some issues when its cold and i am suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and checking
solder joints or such. But, i don't not have a spare and do not want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line successfully?
Any pictures internally if you did? Any tips? This is a OBDII unit.

BOB



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[BOB URZ]

David wrote:

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.

Is the bottom of the board hard potting, or just the semi flexible
coating? Do you know, or are you guessing what's on it?

The problem i am having on the 96 is when it very cold, i get a
error code that the IAT air temp sensor is full scale. The thermistor looks
ok and the connector on the thermistor looks fine. I connected and
put cramolin on the computer connectors. So it seems to be a thermal
condition. Other sensors use the same ground as the IAT, and i am
not getting a code off of them (so i assume the grounding is not an issue)
Though not impossible, i doubt the thermister in the air intake is
thermally intermittent. I sure would like to see what the inside of
the computer looks like before i attempt to take mine off and disassemble it.
I smell a bad solder connection somewhere.

BOB

The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

There is also a good chance the grounds (any of about 6 or 7) could be bad.

The GM computer is a very low failure item, look to it last for your
problem.

David

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message
news:3F804DED.88A00550@inetnebr.com...
My 96 S10 seems to have some issues when its cold and i am suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and checking
solder joints or such. But, i don't not have a spare and do not want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line successfully?
Any pictures internally if you did? Any tips? This is a OBDII unit.

BOB



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[Franc Zabkar]

On Sun, 5 Oct 2003 12:44:31 -0500, "David" <dkuhajda@locl.net.spam>
put finger to keyboard and composed:

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.

The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

I would think that the computer should be spec'd for operation right
down to cranking voltage (9V or less?).


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Jeff]

Most of the GM ones I have looked at were a pain
to dissassemble without damaging something that
only a reman center would have and then after that
I found nothing noticable wrong inside.
Jeff

"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F8061B5.D2460352@inetnebr.com...

David wrote:

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.


Is the bottom of the board hard potting, or just the semi flexible
coating? Do you know, or are you guessing what's on it?

The problem i am having on the 96 is when it very cold, i get a
error code that the IAT air temp sensor is full scale. The thermistor
looks
ok and the connector on the thermistor looks fine. I connected and
put cramolin on the computer connectors. So it seems to be a thermal
condition. Other sensors use the same ground as the IAT, and i am
not getting a code off of them (so i assume the grounding is not an issue)
Though not impossible, i doubt the thermister in the air intake is
thermally intermittent. I sure would like to see what the inside of
the computer looks like before i attempt to take mine off and disassemble
it.
I smell a bad solder connection somewhere.

BOB


The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

There is also a good chance the grounds (any of about 6 or 7) could be
bad.

The GM computer is a very low failure item, look to it last for your
problem.

David

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message
news:3F804DED.88A00550@inetnebr.com...
My 96 S10 seems to have some issues when its cold and i am suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and checking
solder joints or such. But, i don't not have a spare and do not want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line successfully?
Any pictures internally if you did? Any tips? This is a OBDII unit.

BOB



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[David]

Nope, they are not. During cranking the computer is not operating in any
kind of closed loop mode. The voltage references for all the run sensors
require a full battery voltage. Only a couple of digital sensors are used
during start up, oil pressure switch, crank and/or cam sensor. The computer
does not need any of the analog circuits to be operating during start up.

Back the to question, the Air temp sensors on GM cars are very problem
prone. It is highly possible it could be intermittent when cold.

No I am not guessing on the GM computers. All of them I bothered to take
apart had both a soft rubbery coating on a large part of it and a hard
potting on part of the computer board.

At least the battery problem should be easy to figure out, a good voltmeter
right before and after a cold start up. The cigarette lighter is an easy
place to double check the voltage.

The sensor in question also should be verified per the troublshooting guide
in the vehicle service manual. If you do not have it, I think alldatadiy
gives the same troublshooting guides online, first purchase is $25 for one
year use.

David

Franc Zabkar <fzabkar@optussnet.com.au> wrote in message
news:2311ovg1kc6fd78l2fkfae4h34sp4g1mp6@4ax.com...

On Sun, 5 Oct 2003 12:44:31 -0500, "David" <dkuhajda@locl.net.spam
put finger to keyboard and composed:

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.

The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

I would think that the computer should be spec'd for operation right
down to cranking voltage (9V or less?).


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[BOB URZ]

Jeff wrote:

Most of the GM ones I have looked at were a pain
to dissassemble without damaging something that
only a reman center would have and then after that
I found nothing noticable wrong inside.
Jeff

That's the kind of info i am trying to find out. Without a spare handy, i
don't want to disable my truck. I sure would like a donor to play with
before i did the real thing.

And yes, i do have the factory shop manuals. They are good only up to
a point where your brain has to take over to fill in the blanks.

This problem with he IAT (Intake air sensor) only happens when its
very cold. ANd it only sets one code when it happens. And other sensors
share the same ground with this one and no other codes are set. So i know
the grounds are ok. Connectors seems to be ok and i shot D5 into them.
This thermistor shows a full scale code error, so the hot wire to it
is either open or shorted when very cold, or it has a bad solder connection
or component in the CPU that's driving it. It has not got that cold yet,
but the clock is ticking.....
And i refuse to pay hundreds of dollars for a remanufactured one
not knowing if that will solve the problem.

I need to get me a autotap kit to go with my laptop.


BOB

"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F8061B5.D2460352@inetnebr.com...


David wrote:

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.


Is the bottom of the board hard potting, or just the semi flexible
coating? Do you know, or are you guessing what's on it?

The problem i am having on the 96 is when it very cold, i get a
error code that the IAT air temp sensor is full scale. The thermistor
looks
ok and the connector on the thermistor looks fine. I connected and
put cramolin on the computer connectors. So it seems to be a thermal
condition. Other sensors use the same ground as the IAT, and i am
not getting a code off of them (so i assume the grounding is not an issue)
Though not impossible, i doubt the thermister in the air intake is
thermally intermittent. I sure would like to see what the inside of
the computer looks like before i attempt to take mine off and disassemble
it.
I smell a bad solder connection somewhere.

BOB


The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

There is also a good chance the grounds (any of about 6 or 7) could be
bad.

The GM computer is a very low failure item, look to it last for your
problem.

David

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message
news:3F804DED.88A00550@inetnebr.com...
My 96 S10 seems to have some issues when its cold and i am suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and checking
solder joints or such. But, i don't not have a spare and do not want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line successfully?
Any pictures internally if you did? Any tips? This is a OBDII unit.

BOB



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[k_teppo]

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message news:<3F804DED.88A00550@inetnebr.com>...

My 96 S10 seems to have some issues when its cold and i am suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and checking
solder joints or such. But, i don't not have a spare and do not want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line successfully?
Any pictures internally if you did? Any tips? This is a OBDII unit.

BOB

Sorry in advance for the slight off-topic
Bob, for your consideration:

I have heard of numerous problems with GM's computers/proms. Most are
late-80's early 90's, but the same could apply for mid-90's. I had a
1989 Oldsmobile Cutlass Ciera 3.3L that ran very poorly. A mechanic
scanned for codes and it was found that the coolant temp. sensor was
reading full hot ALL the time. This mechanic changed the sensor (and a
few other sensors) and it didn't solve the problem. I decided I would
finish the repair. I went to the scrapyard and picked up a replacement
computer (with prom). I swapped the proms and put in the new computer.
SAME PROBLEM. Swapped proms, and it ran like it should. Corrupted
proms do weird things.
Another nearly identical issue was with my co-worker's 1991 Olds
Cutlass Supreme. The car ran poorly and smelled of gasoline. If he
didn't keep it revving, it would flood out and die. He swapped out
sensors from a wreck to no avail, and once again, swapping PROMs fixed
the issue. Seems the corrupted prom was keeping the fuel injectors
open either constantly, or just too long.

BTW: the computer on most of these vehicles is located behind the
glovebox. I'm sure you know this, but when removing the prom, keep in
mind that they are **particularly** sensitive the ESD.

One last note: I opened both computers and found no potting compound
and all solder joints looked great.

Take care and good luck with your repair!
-k

 

[Asimov]

"Franc Zabkar" bravely wrote to "All" (06 Oct 03 06:54:01)
--- on the heady topic of "Re: GM Computers"

FZ> From: Franc Zabkar <fzabkar@optussnet.com.au>
FZ> Subject: Re: GM Computers
FZ> Organization: Bachelor Life Ltd
FZ> Reply-To: fzabkar@optussnet.com.au
FZ> Xref: aeinews sci.electronics.repair:7512

FZ> On Sun, 5 Oct 2003 12:44:31 -0500, "David" <dkuhajda@locl.net.spam>
FZ> put finger to keyboard and composed:

You have to have the equipment to remove the potting compound off the
circuit board before you can do anything with it.

The connectors getting corrosion is a very common problem. Also a weak
battery or slightly low voltage will cause all kinds of erratic symptoms
(especially when cold). Battery MUST be over 12v for proper computer
operation.

FZ> I would think that the computer should be spec'd for operation right
FZ> down to cranking voltage (9V or less?).

I saw a commercial gadget today which plugs into the cigarette lighter
to preserve the computer data when the battery is removed. Basically it
consists of a small 9 volt battery with what I presume is a series diode
and with an accessory plug on the end of the cable. So obviously the
data can be preserved even for a voltage slightly less than 9 volts.

Asimov
******

.... Over a hundred billion electrons were used in crafting this tagline.

 

[Jeremy D. Grotte]

In reference to the IAT error when cold...
I know it seems practically impossible, but I've had 2 bad ones in the last
couple of years, one on a '93 Geo Metro, the other on a '89 Grand Prix. I
made a quicky test rig consisting of a 9v battery, load resistor, and the
IAT and my o-scope. I pulled the IAT out, and sure enough, when I'd cool it
down and smack it around a bit, the one from the Metro would go open, the
one from the Grand Prix would go shorted. I can only guess that the
thermistor internally broke down somehow, like a really big cold solder
joint in the sensor itself.

My .2 cents worth...
JDG

"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F810943.E71BF270@inetnebr.com...

Jeff wrote:

Most of the GM ones I have looked at were a pain
to dissassemble without damaging something that
only a reman center would have and then after that
I found nothing noticable wrong inside.
Jeff


That's the kind of info i am trying to find out. Without a spare handy, i
don't want to disable my truck. I sure would like a donor to play with
before i did the real thing.

And yes, i do have the factory shop manuals. They are good only up to
a point where your brain has to take over to fill in the blanks.

This problem with he IAT (Intake air sensor) only happens when its
very cold. ANd it only sets one code when it happens. And other sensors
share the same ground with this one and no other codes are set. So i know
the grounds are ok. Connectors seems to be ok and i shot D5 into them.
This thermistor shows a full scale code error, so the hot wire to it
is either open or shorted when very cold, or it has a bad solder
connection
or component in the CPU that's driving it. It has not got that cold yet,
but the clock is ticking.....
And i refuse to pay hundreds of dollars for a remanufactured one
not knowing if that will solve the problem.

I need to get me a autotap kit to go with my laptop.


BOB




"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F8061B5.D2460352@inetnebr.com...


David wrote:

You have to have the equipment to remove the potting compound off
the
circuit board before you can do anything with it.


Is the bottom of the board hard potting, or just the semi flexible
coating? Do you know, or are you guessing what's on it?

The problem i am having on the 96 is when it very cold, i get a
error code that the IAT air temp sensor is full scale. The thermistor
looks
ok and the connector on the thermistor looks fine. I connected and
put cramolin on the computer connectors. So it seems to be a thermal
condition. Other sensors use the same ground as the IAT, and i am
not getting a code off of them (so i assume the grounding is not an
issue)
Though not impossible, i doubt the thermister in the air intake is
thermally intermittent. I sure would like to see what the inside of
the computer looks like before i attempt to take mine off and
disassemble
it.
I smell a bad solder connection somewhere.

BOB


The connectors getting corrosion is a very common problem. Also a
weak
battery or slightly low voltage will cause all kinds of erratic
symptoms
(especially when cold). Battery MUST be over 12v for proper
computer
operation.

There is also a good chance the grounds (any of about 6 or 7) could
be
bad.

The GM computer is a very low failure item, look to it last for your
problem.

David

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message
news:3F804DED.88A00550@inetnebr.com...
My 96 S10 seems to have some issues when its cold and i am
suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and
checking
solder joints or such. But, i don't not have a spare and do not
want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line
successfully?
Any pictures internally if you did? Any tips? This is a OBDII
unit.

BOB



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[BOB URZ]

"Jeremy D. Grotte" wrote:

In reference to the IAT error when cold...
I know it seems practically impossible, but I've had 2 bad ones in the last
couple of years, one on a '93 Geo Metro, the other on a '89 Grand Prix. I
made a quicky test rig consisting of a 9v battery, load resistor, and the
IAT and my o-scope. I pulled the IAT out, and sure enough, when I'd cool it
down and smack it around a bit, the one from the Metro would go open, the
one from the Grand Prix would go shorted. I can only guess that the
thermistor internally broke down somehow, like a really big cold solder
joint in the sensor itself.

My .2 cents worth...
JDG

Thank for the insight. I find that very interesting. I suppose i will try a new
one
if the code pops again and see what happens. I have never seen one
fail in that manor before.

BOB

"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F810943.E71BF270@inetnebr.com...


Jeff wrote:

Most of the GM ones I have looked at were a pain
to dissassemble without damaging something that
only a reman center would have and then after that
I found nothing noticable wrong inside.
Jeff


That's the kind of info i am trying to find out. Without a spare handy, i
don't want to disable my truck. I sure would like a donor to play with
before i did the real thing.

And yes, i do have the factory shop manuals. They are good only up to
a point where your brain has to take over to fill in the blanks.

This problem with he IAT (Intake air sensor) only happens when its
very cold. ANd it only sets one code when it happens. And other sensors
share the same ground with this one and no other codes are set. So i know
the grounds are ok. Connectors seems to be ok and i shot D5 into them.
This thermistor shows a full scale code error, so the hot wire to it
is either open or shorted when very cold, or it has a bad solder
connection
or component in the CPU that's driving it. It has not got that cold yet,
but the clock is ticking.....
And i refuse to pay hundreds of dollars for a remanufactured one
not knowing if that will solve the problem.

I need to get me a autotap kit to go with my laptop.


BOB




"BOB URZ" <"sound(remove)"@inetnebr.com> wrote in message
news:3F8061B5.D2460352@inetnebr.com...


David wrote:

You have to have the equipment to remove the potting compound off
the
circuit board before you can do anything with it.


Is the bottom of the board hard potting, or just the semi flexible
coating? Do you know, or are you guessing what's on it?

The problem i am having on the 96 is when it very cold, i get a
error code that the IAT air temp sensor is full scale. The thermistor
looks
ok and the connector on the thermistor looks fine. I connected and
put cramolin on the computer connectors. So it seems to be a thermal
condition. Other sensors use the same ground as the IAT, and i am
not getting a code off of them (so i assume the grounding is not an
issue)
Though not impossible, i doubt the thermister in the air intake is
thermally intermittent. I sure would like to see what the inside of
the computer looks like before i attempt to take mine off and
disassemble
it.
I smell a bad solder connection somewhere.

BOB


The connectors getting corrosion is a very common problem. Also a
weak
battery or slightly low voltage will cause all kinds of erratic
symptoms
(especially when cold). Battery MUST be over 12v for proper
computer
operation.

There is also a good chance the grounds (any of about 6 or 7) could
be
bad.

The GM computer is a very low failure item, look to it last for your
problem.

David

BOB URZ <"sound(remove)"@inetnebr.com> wrote in message
news:3F804DED.88A00550@inetnebr.com...
My 96 S10 seems to have some issues when its cold and i am
suspecting
some potential problems with the computer under the hood.
Normally, i would have no problem with tearing one apart and
checking
solder joints or such. But, i don't not have a spare and do not
want
this to
be a one way trip. Anyone tore down a mid 90's Gm vehicle computer
soldered it up and inspected it, and put it back on line
successfully?
Any pictures internally if you did? Any tips? This is a OBDII
unit.

BOB



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