Re: The dreaded check engine light


"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message
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"Reasoned Insanity" <mintclovers@@yahoo.com> wrote in message
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"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message
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"Reasoned Insanity" <mintclovers@@yahoo.com> wrote in message
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"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message
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"Reasoned Insanity" <mintclovers@@yahoo.com> wrote in message
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I finally got one on my 95 Geo Prizm LSI. It's the first one I've ever
had on a car and I'm already panicky. Strangely it coincided with my
running the car almost out of gas and I was wondering if that could
have anything to do with it. I had less then a half gallon left when I
refueled. I wanted to see if I could push this tank of gas to 400
miles, but I never imagined that could make my check engine light go
on; if indeed that is the culprit.

No need to panic just because you got a check engine light. I doubt
if running the car almost out of gas has anything to do with the check
engine light, but FYI, it is not a good idea to run the car low on gas
because you can end up with drivability problems or a ruined fuel pump
or clogged fuel filter.

The 1995 Geo Prizm does not have the OBD II diagnostic system so the
good news is, you do not need an OBD II code scanner to pull codes,
all you need is a paper clip. The bad news is, the trouble codes are
not universal so you will need some kind of manual to interpret the
codes.

To pull codes, un-bend the paper clip and connect terminals TE-1 and
E-1 in the diagnostic port and switch the ignition key to the on
position without starting the car. Count the flashes of the check
engine light - you will notice a pattern of flashes and short and long
pauses. For example, with "X" being a flash and "P" being a short
pause and "PP" being a longer pause:

XXXX P XX PP XXXX P XXXX would be trouble codes 42 and trouble codes
45. If there is only one code, the pattern will repeat. A continuous
steady flash means that no codes are stored in memory.

To clear the check engine light, pull the EFI fuse or disconnect the
negative battery cable for 20 seconds or more.
--

Ray O
(correct punctuation to reply)


3 broken paperclips later....

If you're having trouble sticking a paper clip into a test port, you
must have heeded your parent's warning never to stick anything into an
outlet! ;-)

Old war story... A customer once saw me pull a code with a paper clip,
and he was appalled that his expensive car didn't need some fancy
special service tool to pull the code. After that encounter, I made up
a jumper wire with male spade ends so that it looked a little more
official.

Ok, from the looks of it I'm getting the code 71 (or 17 and that's not
in the book) which the books says is the EGR System. the next question
I have is, what is the EGR system and how serious is it? From what the
Haynes says, it's some sort of temperature system. After that, I have
no clue where to go.


The exhaust gas recirculation (EGR) system takes some exhaust gas and
routes it into the intake to be mixed with the air/fuel mixture during
above-idle operation. This reduces combustion chamber temperatures,
which reduces production of oxides of nitrogen, or NOx.

This is a pretty good article that explains EGR operation:
http://www.advanceautoparts.com/english/youcan/html/ccr/ccr20040501e1.html

The EGR in the picture is the saucer-shaped thing with "XL" embossed.

An easy way to test EGR operation is to look at the vacuum hose attached
to the EGR and follow the vacuum hose back to the vacuum switching
valve. Very carefully pull the vacuum hose off of the vacuum switching
valve (careful, the plastic connection may be brittle and break easily),
stick your finger over the port on the vacuum switching valve, and with
the engine idling, suck on nthe vacuum hose. The engine should start to
run rough. If the engine runs normally when you are sucking on the EGR
vacuum hose, then you probably need a new EGR valve.

If the engine does run rough, then take note of the suction on the
vacuum switching valve port when the engine is idling. When you rev up
the engine, it should suck harder on your finger tip.

After that, you will have to follow the EGR diagnosis section in a
repair manual.

By the way, thanks for all the help guys. While I am rather clueless
when it comes to cars, I am still wanting to try to learn about the
inner workings of them.

You're very welcome! My hat is off to anyone who is willing to get
their hands a little dirty and learn!
--

Ray O
(correct punctuation to reply)


It might take me a few days to figure out how to get this fixed; if it is
indeed the problem. Is my car still safe to drive?

You may be able to remove the EGR valve and clean it up a bit, but it is
probably a stopgap measure if the EGR is clogged.

Yes, if the EGR is the only problem.
--

Ray O
(correct punctuation to reply)


From the looks of it, there are 3 vacuum hoses attached to my EGR, two going
in one side of the top and a third one going in the other side. There is
also another line coming out the bottom of it but it's a solid line and not
a hose. Which is the line I am wanting to pull?


One thing interesting to note is that the valve says densco on it. I thought
the Geo's were made with delco parts,


.

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