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94 Grand Am 3.1 V6 SES light
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CarKEY
New User
Mar 10, 2005, 11:56 PM
Post #1 of 4
(7138 views)
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94 Grand Am 3.1 V6 SES light
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My service engine soon light started coming on. It comes on about 15 minutes into my commute to work. Oddly it only seems to happen on the highway. Car seems to be running fine, and if I pull over and restart the car the light will usually be off. I went to autozone to try and get the code read, but I guess my year grand am has a computer that they can't get a code out of easily. I'll probably have to find a shop that can. My best edjucated guess is its the Oxygen sensor going bad. Anyone want to second that, or has a better idea of what it might be?
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DanD
Veteran
/ Moderator
Mar 11, 2005, 8:13 AM
Post #2 of 4
(7131 views)
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Re: 94 Grand Am 3.1 V6 SES light
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With out having the code it’s anybody’s guess, but with you saying only on the highway my guess would be something with the EGR system.
The ECM will randomly do a functional test on the EGR system and the vehicle has to be above a certain speed before it will perform this test.
That’s my only reasoning for the guess.
What happens is when the criteria is met the ECM will command the EGR to open. The ECM then watches for a reaction from either the O2 or MAP sensor. IF the ECM doesn’t see the reaction it’s expecting on comes the light.
With your car still being OBD 1 the light will go out on a restart because the ECM hasn’t had a chance to run a functional test yet.
Dan.
Canadian "EH"
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CarKEY
New User
Mar 11, 2005, 9:42 PM
Post #3 of 4
(7121 views)
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Re: 94 Grand Am 3.1 V6 SES light
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Thanks Dan. If that turns out to be the trouble, what can I expect a repair would cost me?. I'm going to bring the car in tomarrow to get the code read.
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DanD
Veteran
/ Moderator
Mar 12, 2005, 7:08 AM
Post #4 of 4
(7118 views)
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Re: 94 Grand Am 3.1 V6 SES light
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It’s still to soon to tell what the costs would be, even after the code is retrieved there will still be more diagnostics needed to find the root problem.
A lot of people think that a code takes you right to the problem and you just change out the sensor or what ever the code points to. What a code actually does is to tell us what input or output circuit has a fault, that could mean a sensor, wiring ECM or nothing at all to do with that circuit but the code was set through a chain reaction from a different circuit or device.
For example if the code in your car turns out to be an EGR code, you test the EGR system and it is functioning properly, but you notice that the O2 sensor is not reacting when the EGR valve is opened. The O2 is still functioning with in its perimeters and hasn’t set a code, but it is not capable of making the swing in voltage that the ECM is expecting to see when it runs an EGR test. The ECM doesn’t know any better and sets an EGR code even thou the actual fault is the O2.
Hope this made some form of sense, it’s hard to explain.
Dan.
Canadian "EH"
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