91 Subrb 4x4 350 Scanner

I have a 1991 Suburban 350 TBI 4x4. I'm looking for a scanner to plug into the diagnostic port to give me enginge problem codes.
Can anyone suggest a good unit that won't empty my wallet but is still
a solid unit?
Also whats a good source for a chiltons type manual online? Is Chiltons the best one to go with.
The truck starts but after a minute or so it starts to stumble and will hardly idle. I'm suspecting the ECM but I need to find out for sure.
Thanks for any help Bob
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Butter,
A paperclip will do just fine to get the codes.
http://www.georgiasyty.com/aldl.htm
Doc
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. . ========
I have a 1991 Suburban 350 TBI 4x4. I'm looking for a scanner to plug into the diagnostic port to give me enginge problem codes.
Can anyone suggest a good unit that won't empty my wallet but is still a solid unit?
Also whats a good source for a chiltons type manual online? Is Chiltons the best one to go with.
The truck starts but after a minute or so it starts to stumble and will hardly idle. I'm suspecting the ECM but I need to find out for sure.
Thanks for any help Bob Butter, ======== snipped-for-privacy@nope.com (Doc) replied:
A paperclip will do just fine to get the codes.
http://www.georgiasyty.com/aldl.htm
Doc ==========what The Doc said.....ditto.
as far as an online source for tech data, I would HIGHLY suggest going with ALLDATA for vehical specific information. You could always access the Dealer Tech site, but they charge for a day....what ALLDATA charges for a years subscription.
ALLDATA LLC - Leader in Automotive Information Address:http://www.alldata.com/
with a paper clip and good tech info.... you won't need a scanner. A Flute meter comes in handy though.
MarshMonster ~:~ ====
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On Fri, 22 Oct 2004 10:22:59 GMT, Fatty McButterpants
Thanks Marsh Monster and Doc. You really saved me some money on the auto repair guy so far!
I have a few more questions.
1991 Suburban 350 TBI 4x4 The code return a code 15. According to the web link "Coolant Sensor - Low Temp - Fix overheating problems, if any. Check all wiring to coolant sensor. Replace coolant sensor."
This is what its doing. It starts and idles like a champ. After about 5 minutes at idle it begins to stumble and will not idle and will die if you don't tap the gas pedal. Even at that it is very hard to keep it running! Does a bad "Coolant Sensor" cause this type of problem?
I'm asking this to confirm it could be the problem and not a screwy code from the ALDL.
Question 2. Is there an online guide to replacing this coolant sensor?
Question 3. Can I test the coolant sensor with a multimeter and if so what resistance reading will confirm its bad.
My other truck is a 1979 chevy silverado 1/4 ton P/U with almost 300k miles and I just love how simple it is to work on!
Thanks for any more help Bob
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Inline...............
wrote:

No problem.

Code 15 is usually set when the connection to the CTS or the CTS itself is shot. The CTS measures resistance and the ECM translates the resistance values into temps. As temp INCREASES, resistance DECREASES. If the CTS is shot or if the connection is bad the ECM will see infinite or extremely high resistance, assume the engine is dead cold and run a super rich mixture to compensate. This causes a shittly idle and poor fuel economy once she warms up. Cold engines like it rich, warm engines do not.

When it starts bumbling and stumbling, does the exhaust smell like unburned gasoline? When you tweak the throttle to keep her running is there any black smoke coming out the tailpipe?

No, the code is correct, it's the cause that is in question. It could be caused by bad CTS or bad CTS harness, which has a tendency to corrode over time. It could also be a fuel overdelivery problem that is causing the engine to run so rich that it just doesn't heat up.

That would be me................ See below. ;-)

Yes you can test it. E-mail me and I will send you the chart of temps and expected resistance values. gmc_man(at)adelphia(dot)net

If this were my truck I'd just skip the testing and replace both the CTS and the CTS harness. Both items will run you under $20 and it's 90% likely that this is your problem. If you're a frugal fellow, go ahead and test it.................
1. CTS is located just to the left of the thermostat housing. Will have a 2-wire harness running to it with one black and one yellow wire. 2. Unplug the harness and use a deep socket to remove the sensor. 3. Screw in the new sensor. You can use a thin layer of teflon tape on the threads to ensure a dry fit. Most new CTS's will come with pipe dope already on the threads. 4. Get a new CTS weatherpack connector. Available only at Autozone. $9.95 Cut the old one off, splice the new one in, using solder and heatshrink tape to do the job correctly. 5. Plug it back in.
Done.
Doc

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Hi; thanks for the "paperclip diagnostic tool" link. I've been trying it, but not having success! (See my thread "Electronic Control Module / ALDL (lack of) Codes") When I try to get the codes, the signal from the ALDL just seems to run out of power. The first couple of 12 codes flash ok, then the (SERVICE ENGINE SOON) light goes dim, for the third 12 code flash; then there's an almost visible, very faint, attempt to flash something else (indecipherable). It just seems to run out of juice. Then, when I turn the key off, remove the paperclip, reinstall the paperclip (making sure I have good contact) and turn the key on and try again: no flashes at all! If I take it for a drive, and try again in an hour or so, it's back to the first sequence (attempting to flash the initial 12 sequence). I've replaced the paperclip with a piece of solid copper wire (ground wire from electrical wiring).....same result! I am using the A and B terminals; there's lots of power in the battery. It seems like there's not enough power coming through the ALDL (or not enough ground?). Any suggestions? I can pick up a trouble code tool ($50), but wonder if I'll have any better luck with it?
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Sounds like your ECM is ready to puke on you. Any driveability problems?
Doc

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Hi Doc; The only driveability problem SEEMED to be a fuel delivery problem (see my thread "Electronic Control Module / ALDL (lack of) Codes"); and the performance improved when I replaced the fuel filter, but the "Service Engine Soon" light kept coming on, under load, with fuel tank below 1/2 full. That's when I attempted to get the codes. Other than that, it drives great. Possibly a little fuel smell in the exhaust at first idle when stone cold, but no black smoke, and good smooth acceleration. When I get a chance, I'm going to dig in under the dash and look for the ECM. I don't know anything about ECMs and ALDLs (what little wrench pulling I usually do involves pre 1955 cars and tractors); but I'm going to look for a poor ground. The data seems to be in the ECM, but there's just not enough juice coming through to get it to light up the "Service Engine Soon" light, other than the first two "1 -2" codes. What do you think....if I jump from the B (Diagnostic Terminal) at the ALDL, directly to ground; that should do the same as jumping from A to B, except it should eliminate any error in bad ground at the ECM....do you think I'll fry the ECM? Keith.
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. . ===== ===== snipped-for-privacy@nospam.sympatico.ca (stude-ious) wrote in message:
<snip>
What do you think....if I jump from the B (Diagnostic Terminal) at the ALDL, directly to ground; that should do the same as jumping from A to B, except it should eliminate any error in bad ground at the ECM....
do you think I'll fry the ECM? Keith. ========== ==========
No.
but........ like "the Doc" said, you may already have a puter going out on you. The light should not be going dim during the proceedure. NEVER!
If the light is going dim during the code retrieval process, I would diagnose that situation first. It's likely to be the cause of all your problems. Running a "known good" ground wire to the ALDL connector terminal B, for no other purpose than to pull codes, is NOT going to cure a thing and is NOT going to confirm the CAUSE of the symptom, and is most likely not going to do anything other than provide an extra step in the diagnostic process. (it's not going to lead you anywhere)
Check resistance to ground at the "A" terminal before you do anything.
~:~ Marsh ~:~
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Hi SwampGas; Sorry I didn't reply right away; we've been dealing with a family medical crisis up here; and the Suburban, well it still runs, so it's had to serve "as is". Thanks for the advice; I'll check the resistance at the "A" terminal. My purpose in jumping to ground at the ALDL was not only to pull codes, but to attempt to trouble shoot a possible bad ground at the "brain". Anyway, I'll have a quick look, and see what I find. Geez, I'd better move into the shop to do it, I just looked out the window, and it's REALLY SNOWING! Looks like an early Canadian winter......better get that Suburban fixed..will soon need the 4WD. Keith.
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Hi Marshy:
Sometimes I think you're only joshing us about your shroom juice!
You actually post good info!
Now about that growth on your Arse. I uess Doc was right, it wasn't terminal. I'm glad, so I can pick on you for years to come.
Good seeing you around!
Refinish King
(stude-ious) wrote in message:
<snip>
What do you think....if I jump from the B (Diagnostic Terminal) at the ALDL, directly to ground; that should do the same as jumping from A to B, except it should eliminate any error in bad ground at the ECM....
do you think I'll fry the ECM? Keith. ================== No.
but........ like "the Doc" said, you may already have a puter going out on you. The light should not be going dim during the proceedure. NEVER!
If the light is going dim during the code retrieval process, I would diagnose that situation first. It's likely to be the cause of all your problems. Running a "known good" ground wire to the ALDL connector terminal B, for no other purpose than to pull codes, is NOT going to cure a thing and is NOT going to confirm the CAUSE of the symptom, and is most likely not going to do anything other than provide an extra step in the diagnostic process. (it's not going to lead you anywhere)
Check resistance to ground at the "A" terminal before you do anything.
~:~ Marsh ~:~
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===== ===== Re: 91 Subrb 4x4 350 Scanner (update) Group: alt.autos.4x4.chevy-trucks Date: Wed, Oct 27, 2004, 10:15am (CST+6) From: snipped-for-privacy@swbell.net (FattyMcButterpants)
wrote:
I have a few more questions. 1991 Suburban 350 TBI 4x4
The code return a code 15.
According to the web link "Coolant Sensor - Low Temp - Fix overheating problems, if any. Check all wiring to coolant sensor. Replace coolant sensor." This is what its doing. It starts and idles like a champ. After about 5 minutes at idle it begins to stumble and will not idle and will die if you don't tap the gas pedal. Even at that it is very hard to keep it running!
<series of questions>
Does a bad "Coolant Sensor" cause this type of problem?
Question 2. Is there an online guide to replacing this coolant sensor?
Question 3. Can I test the coolant sensor with a multimeter and if so what resistance reading will confirm its bad.
Thanks for any more help Bob
====== ====== Answers to yer questions..... 1) yes 2) see link below 3) yes, see link below
Repair for CTS Address:http://www.lotuselancentral.com/cts.htm
yw ~:~ Marsh ~:~
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