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Discussion Starter #1 (Edited)
1995 SS Check engine light on/off?

On my 1995 Impala which only has 20K miles on it the check engine light comes on once in a while as the engine is running up to operating temperature. Usually it happens on warmer days 20 degrees or so above freezing. After I drive about 2 miles or so, the light comes on, along with the primary cooling fan, but the engine temperature is not up to the operating range yet,then the fan stays on for a while, for another mile or so then the fan goes back off and the check engine light goes out, and the problem does'nt return for the rest of the time I am driving that day. And the temperature does stabilize in the operating range with regular fan operation. I changed the coolant temperature sensor and the relay for the fan, Thermostat, and checked all the wiring connections for tightness.
Also what would be the correct engine diagnostic tool to use on the 1995 Impala?
Any Ideas?
:confused:
 

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Any OBD-I diagnostic computer would help in solving the problem. You will need to get one that will read and give you the code while the check engine light is on. You may want some else to drive the car while you use the computer and find what trips the engine service light on. Once the light goes out the fault code is lost.

It is possible that the O2 Sensor is going bad or maybe the Ambient Air Temp sensor, but only the diagnostic computer will help for this problem.
 

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Discussion Starter #3
I appreciate your advice, but why would the O2 sensor or the ambient air sensor being defective cause the cooling fan to come on too soon? Maybe because if the engine thinks the incoming air is too hot it sends an alarm for the check engine light to come on and starts emergency cooling? And for the O2 sensor being bad, why would that cause the fan to come on too soon?
I have the all the complete service manuals for the car so any higher technical info to check the sensors would be well understood.
Thanks.:wink:
 

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Also, codes are stored, and do not delete when the check engine light goes off on these cars.
Stewart
Interesting about these latter OBD-I computers not loosing the code once the light is out. My experience was with the first generation computers that once the light went out the code that tripped the light was also errased. I knew the OBD-II did not loose the code once the light was tripped. Do you have an idea about when the computer was changed to hold the code once the light went out on its own?
 

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By first gen, to you mean the generation that you can use a paper clip to
cause the check engine light to flash a series of flashes, do tell you
what the error code is?
Stewart
Yes I do mean the 82 and up GM OBD-I computers. These early computers would or could loose the fault code once the light went out and/or when the engine was restarted.

I also have the code retrieval key that you described. I also have a Matco Determinator Model MD-2007. This unit can read all American OBD-I computers and most current OBD-II codes as well. I will be looking at buying a Scout 2500 code reader that will also read the new CAN series codes as well.
 

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Discussion Starter #6
Hi, Thanks for all the quick and detailed responses for my question for the Impala, now I am trying to determine which would be the easiest scan tool for me to use, since I was doing some checking online for 2 of them, the autoray ez scan 6000, and the cp 9190 actron. And I was really confused when I was reading the operating instructions for both of them, and add that I never even used one before, I am really lost here.
Any advice on which one would be the one for a novice to use, not trying to change any settings , just want a code reader for the problem.
Thanks :rolleyes:
 

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Discussion Starter #7
Yes Stewart, I was looking @ that tester a couple of days ago on Ebay and almost bought it, but I called the techie over @ Autoxray just to see if it would work on the 95 Impala and he steered me towards this one:

http://cgi.ebay.com/ebaymotors/ws/e...80215225550&ssPageName=ADME:X:RTQ:MOTORS:1123

I am not doubting your word on the easiness of using the auto x ray 6000, it's just that the techie thought that this one, the Actron would be easier for me to use. And to tell you the truth I looked @ the instruction manuals for both of them and they seemed to be the same in cornfusion for me!
Any advice on the more liked one will be my deciding factor in choosing one of the 2.
Thanks Guys.
 

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Might look at Auto Zone and O'Reilly Auto Parts stores, The Scout 2500 I am looking at buying is only 199.99 at O'Reilly auto parts and it scans OBD-I, OBD-II, and the new CAN codes as well, plus you can update it over the enternet for newer cars as they come on the market. Have not used it yet but have been told it is very simple and almost walks you through it.
 

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Discussion Starter #9
Stewart, I took your advice and ordered the Scout 2500 scanner today, it should be arriving here soon and I will let you know what the problem is. I was just thinking offhand that since the car has such low mileage on it and when it does get out the trips are usually 10 miles or less, that the oxygen sensors may be fouled from lack of highway driving to blast them clean? If so I might have an excuse if I get stopped doing 100 mph or so along the highway: Officer I was just blast cleaning out my engine!!!! :eek:
 

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Discussion Starter #10
OK I got the tester Scout 2500 and it's giving me a code DTC 32 For the EGR valve, the vacuum line for it looks good, I did'nt have time for any further checking as of yet, but since it's a short tripper, maybe the exhaust passages are just clogged up? I will investigate further, probably by Friday.
Thanks. :rolleyes:
 

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I will look up this evening about what to test for the EGR. Not always is it the valve itself. It may be in the control system for the EGR. Will write more latter.
 

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my cars got a problem kinda like that i get a check engine light after 10 15 miles usually when im on the brakes and it varys on how long it stays on. the fan kicks in and i get the chenck engine light. the only thing is that every time its on my voltmeter drops if the radios off or on it doesent make a difference same goes for heat A/C anyone ever run into anyhting like that before
 

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Currently it may be a few days before I am back. Had a storm 2 night ago that is causing electrical problems in my home I do not dare plug in my laptop to recharge. The storm blew my wifes computer out.
 

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Discussion Starter #14 (Edited)
I found it, Bad EGR valve, it does'nt hold vacuum, not for the spec. time of 20 seconds, not even 5 seconds, so it's got a bad diaphragm, and it set off the error code to let me know it's bad.
Technology, gotta love it!!!
Any one have a favorite decent pricing parts supplier?
Thanks Guys!
 

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Discussion Starter #15 (Edited)
OK It's been about 2 years now that I had replaced the EGR valve and lo and behold it went bad again,(not holding vacuum) also not really putting that many miles on the car, but the only difference was that it was a replacement valve from PepBoys, not sure of the brand but it was'nt a Standard or a Delphi, which Delphi is original equipt. for this engine.
Mistake getting one from PooperBoys?
As it was only half price of the other 2 thought could get away saving a few bux, guess NOT!!!!
Any thoughts on this? :rolleyes:
 
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