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bennelson 10-21-2008 05:16 PM

HELP! Check engine light - Loss of power
 
My check engine light has been coming on in my '95 4-cylinder Chevy S10.

I believe this truck is PRE-OBD2, as I was never able to get the Scangauge to work with it. (Supposedly, it works on the 6-cylinder '95s!)

How do I get the "check engine light" code from the truck?

I have heard there is a way to jumper two of the pins in the diagnostic connection so that the check engine light flashes a certain number of times, and you get the error code that way.

How do I do this? Which pins do I jump? What else do I need to know?

Thanks in advance!

-Ben

bennelson 10-21-2008 06:43 PM

Grrrr
 
I think my truck has a OBDII-style plug, but uses OBD1 computer and info.

After reading through my Haynes repair manual, and checking out an S10 forum, I have come to the following conclusion:

The '93 and earlier have an ALDL connection. The 94 & 95 have the OBDII style connection, but don't actually HAVE OBDII, and the '96 and newer have OBDII.

It appears that the only way that I can read the Check Engine Light code is with a special reader that will do both ODB & OBDII. The local auto parts store's readers don't do that.

Grrr. - Very frustrating.

2000mc 10-21-2008 08:56 PM

obdII connector means its obdII as far as a scan tool, or jumping pins to flash codes is concerned. its not actually obdII in the sense that some of the '96 requirements may not have been met yet.

HObart 10-21-2008 11:02 PM

Autozone
 
So........My radio tells me that they can scan for codes ( no charge ) and be more than happy to sell you the part that you need..........Never been there and don't know for sure......

bennelson 10-21-2008 11:08 PM

Quote:

Originally Posted by 2000mc (Post 68582)
obdII connector means its obdII as far as a scan tool, or jumping pins to flash codes is concerned. its not actually obdII in the sense that some of the '96 requirements may not have been met yet.

Nope.

Scanguage doesn't work with it. Autozone's trouble-scanner doesn't work with it. It's an odd-ball!

2000mc 10-22-2008 12:30 AM

does the scan tool power up? if not is your cig lighter also inop?

bennelson 10-22-2008 12:33 AM

Scantools just try to communicate with the computer and never can.

My cig lighter works fine.

2000mc 10-22-2008 12:38 AM

tried with a tech2 yet? i'd try to find a dealership thats willing to read codes for ya, ours does that much for free, if a tech2 wont communicate, then theres a dlc/ communications issue you'll have to fix first

3dplane 10-22-2008 12:40 AM

Ben!
Same question: when you say the scanner does not work,does it not even power up or just does not read?
OBD 2 carries its own power supply(orange wire behind plug) OBD 1 needs the scanner powered.
OBD 1 plug is square,OBD 2 plug is (trapezoid kind of) but yes the oddball year will have the new plug but actually OBD 1. At the dealership it is tech 1 for the old one and tech 2 for the new stuff. I don't think it's flashable.
Barna

2000mc 10-22-2008 12:55 AM

btw, i used to own a 94 olds 88. it had a OBDII style connector, worked with a tech2, and not a tech1, used OBDII codes, not manufacturer codes(OBDI style). however i dont recall if i ever had it hooked up to a generic scantool to know if that worked or not.

bennelson 10-22-2008 12:50 PM

Yesterday, I installed a kill switch in the truck.

Today, the CHECK ENGINE LIGHT no longer comes on, but I am having another problem instead!

I have no power when I put the gas pedal down farther than about half-way!

This gives me terrible acceleration, and I can barely make freeway speed. I can slowly accelerate if I am level or slightly downhill.

Uphill, things start slowing down because I can't push the gas pedal down far enough before it starts losing power!

Also, if I rev the engine up real high, when in neutral with the parking brake on, it sort of shutters and snorts.

Is this a "fuel-rich" problem? When I give it gas, it's getting too much gas, and I lose power?

When I installed the kill switch, I cut the wire to the fuel injectors, and added a momentary off relay in-line to it to turn off the engine.

I put a jumper back in so that that wire is connected directly again (no relay) and am still having the same problem.

Please don't tell me that that's a special wire that has very particular resistance that effects the injectors or something like that!!!!!

What could be wrong with the truck?!?!?!

Thanks in advance!

TestDrive 10-22-2008 04:10 PM

Symptoms sound like it could be a dirty MAF (Mass Air Flow sensor).

3dplane 10-22-2008 04:40 PM

Or a clogged catalytic converter but it's a little coincidental with messing with the injectors. Unless somehow it ran rich for a while.
Barna

bennelson 10-22-2008 05:15 PM

I have heard that O2 sensors can get messed up through contamination. One cantaminate can be antifreeze.

I saw that my coolant looked low. Coincidence? or cause?! If cause, how did the coolant get down and mess up my o2 sensor, head gasket leak?

2000mc 10-22-2008 11:17 PM

first guess, i'd lean twards 3dplane and the converter.

with the vehicle in neutral does it seem to rev freely? only take light throttle to rev up, or quite a bit? exhaust sound different than before? good throttle response only at low rpm?

bennelson 10-23-2008 12:37 AM

Quote:

Originally Posted by 2000mc (Post 68801)
first guess, i'd lean twards 3dplane and the converter.

with the vehicle in neutral does it seem to rev freely? only take light throttle to rev up, or quite a bit? exhaust sound different than before? good throttle response only at low rpm?


In Neutral, it revs freely, needing only a light touch. Reving it high makes the engine loud and kinda cough/sputter/chug.

The exhaust does should different than before. More "swooshy".

Throttle response at low RPMs seems good, but not at the more highly depressed end of the throttle.

Metrosexual 10-24-2008 09:46 PM

It sounds like your cat is plugged, catalytic converter that is....
This could cause your check engine light to come on and set a cat efficiency code.
I have never had a communication problem using a Snap-On or Modus Scanner on a '95 S-10 with a 4.3 Vortec and an OBD II style connector. There may be an electrical problem in the wiring between your vehicle computer and the OBD II connector.
I think your going to have to have this problem diagnosed by a qualified tech, as it sounds like there are several things going on.
One thing you can check is all your fuses. There are several ECM (vehicle computer) fuses. I'm not certain if a blown fuse would cause your communication problem, but it wouldn't hurt to check.

bennelson 10-24-2008 10:02 PM

The '95 6 cylinder has OBD2, the 4 cylinder doesn't! Still has the same style connector though!

3dplane 10-25-2008 11:44 AM

A quick test for those simptoms and to find out wheter it is the CAT or not is to disconnect the exhaust somewhere between the motor and the CAT.
Crank it up and nail the throttle to see if the "peppyness" is restored.
If nothing else the neighbours will be very impressed....
You will be able to tell if there is difference in one punch of the throttle in neutral. That's how we do it in the shop if in doubt.
Barna

2000mc 11-04-2008 12:24 AM

bennelson - think i spoted something helpful

Some 1995 GM vehicles have the 16-pin connector but have accessible OBD-I codes. Check the underhood emissions sticker to confirm, and if yours is OBD-I, the codes are accessed by bridging terminals 5 and 6

found on Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

bennelson 11-04-2008 07:25 PM

Thanks 2000mc!

I was able to get that to work! I saw how to do it on the older connector, but couldn't find any info on this odd year with the OBD2 style connector!


Once I jumpered those pins and turned the truck on, the check engine light flashed once, then twice, and repeated that three times.

Then it flashed 3 times and two times and repeated that pattern three times total, then started the 1,2 1,2 1,2 ... 3,2 3,2 3,2...

It's my understanding that the truck is giving me the codes for 12 and 32.

According to Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical :
code 32 means
"32 EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas."

So what the heck is an EGR? What's it do? And how do I fix it?


And what about the error code 12? It's not listed on that page!


EDIT: In a list of generic GM OBD2 codes, it says 12 is diagnostic mode and that 32 covers:
BARO sensor circuit(carb models)
EGR circuit(injected models)
MAP sensor(open)

I think we can eliminate the BARO as my truck is fuel injected.

bennelson 11-04-2008 08:11 PM

Currently reading through my Haynes S10 repair manual.

Apparently the EGR (exhaust gas recirculation) is an emissions thing, designed to reduce pollution and make my truck not work right.

The book says the EGR valve is controlled by a vacuum control solenoid valve. That's a remotely operated electronic switch/valve, right?

The book also says that the duty cycle time for that valve is controlled by the computer using info from the ECT, VSS, and IAT sensors.

Does that mean that the problem could be one of the other sensors? If it was, wouldn't it give another error code in the flashing check engine light?

The book also said to check for leaky/bad vac hoses and noted that some models use a BACK-PRESSURE-TYPE EGR valve.

A back-pressure valve might have problems working right if there is something wrong with the exhaust system, right?

Earlier, some people made comments about a possible plugged up catalytic converter or similar problems.

Is all this connected? Is it starting to make sense to anyone?

Learning as I go...

-Ben

bennelson 11-04-2008 09:03 PM

HHmmmm - maybe bad
 
I have potential bad news.

In inspecting the engine, I see wetness oozing from what looks like the spot between the head and the rest of the engine.

The coolant in the expansion tank looks dirty.

Do I have a leak in the head gasket, causing the oil and coolant to mix, and cause these other problems?

2000mc 11-05-2008 12:34 AM

12 is something like no camshaft position sensor signal or something like that... they all show it as a current code when the engine isnt running

the egr...well youre pretty much going to have to diag. that. sensors not directly related to the egr system i would consider unlikely causes. more likely would be the valve itself, vacuum leak in the hoses controlling the egr, solenoid, or it seems like theres a egr temp sensor , atleast on some, blocked passages...

head gasket leaks could cause a laundry list of problems...

Ford Man 11-05-2008 09:06 AM

Quote:

Originally Posted by bennelson (Post 70890)
I have potential bad news.

In inspecting the engine, I see wetness oozing from what looks like the spot between the head and the rest of the engine.

The coolant in the expansion tank looks dirty.

Do I have a leak in the head gasket, causing the oil and coolant to mix, and cause these other problems?

If I was concerned about the head gasket I'd refill the cooling system with 50/50 water anti freeze solution and watch it for a few days, if it lowers the coolant level within a few days I would be very suspicious of the head gasket, but before jumping to the conclusion it's the head gasket check to make sure you don't have any leaks around the radiator cap, thermostat housing, in the radiator, or leaking radiator hoses/heater hoses. Another thing you could do is drain the oil and check for coolant in the oil. Have you noticed excessive steam from the tail pipe? If so that's probably the engine burning the coolant. Another forum I am a member of is www.gassavers.org there are several pretty knowledgeable people there that might have some suggestions too.

3dplane 11-05-2008 10:55 PM

Ben!
You are dang right assuming theyare all connected.
And that is why it's not easy to fix over the internet.
Regardless of the type of EGR valve used if it is vacuum controlled it will not be able to operate with a clogged CAT (or muffler)because the engine is unable to produce enough vacuum.
How hard is it for you to disconnect the exhaust?(rust etc). Seriously that would be the easiest way to find out. By the way a stuck closed EGR valve will not effect drivability.
A stuck open EGR will only effect the way the engine runs (like crap) at low rpms. And that is actually one way to see if the EGR passage is clogged or not to open the valve (either manually on the old or command open with the scanner on newer) and if the engine dies from idle,all is good.
I'm just going by your simpthoms description.
Barna

bennelson 06-16-2009 11:01 PM

Oh No!

These same loss of power symptoms are back!

I had to come back here and dig around to find this thread to see what I ever did as a solution to the problem!

There never was one?
It seems the problem just sort of cured itself seven months ago when it was an issue.

I do seem to remember sort of a rattle going on before all this started again. I think the sound was from the catalytic converter!?!? Could a "clogged cat" do that?

Christ 06-16-2009 11:15 PM

Clogged/burned cat could cause serious loss of power, overheating, etc..

Disconnect your exhaust before the cat, fire it up, and rev'er up a bit... see if it stops that from happening.

If it does, remove the cat completely, and shine a light through it. You should be able to faintly see light at the other end. Do it in a dark place, so you'll see better. Shake the cat while it's off... if anything rattles, it's bad, unless the rattling noise is just the heat shield.

bennelson 07-07-2009 07:13 PM

OK, we have finally reached a conclusion on this whole mysterious issue.

My last comment on this was a few weeks ago.
I just got back from a trip, then had to run off to the MREA Energy Fair, and have been busy since then.

Right before taking off for the energy fair, I quick went to work on my exhaust system.

After 20 minutes of wacking, slashing, and whatever else I could do to get the exhaust, muffler, and catalytic converter off there, I had the muffler in my hands and it made a rattling noise!

Want to guess what was inside?

Here's a hint:
http://gallery.me.com/benhdvideoguy/...12470038520001

Apparently, a couple of chunks of catalytic converter broke loose and then wedged themselves inside the intake end of the muffler. Notice that the once piece at least has the holes going the right direction, but the other is at a right angle!

This must have been the equivelant of a potato in the tailpipe!

I still need to completely remove the cat and replace it with some plain straight pipe to keep any more chunks from breaking off and getting into the muffler again.


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