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Discussion Starter #1
i got a 91 silverado and whenever it flashes the codes i get a series of 1 flash then 2 flashes, and also 3 flashes then 2 flashes, can anybody tell me what these codes mean or where i can go to find out?
 

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Resident Guinea Wop
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Yeah, the 1 - 2 = 12

Normal. Always does this.

The 3 - 2 = 32

EGR system. EGR open command did not change MAP sensor signal. Normal EGR flow should cause slight decrease in manifold vacuum which would change MAP sensor signal.

Most likely is that your EGR valve has siezed up. Inspect the vacuum lines going to it.. If all looks good, replace the sucker.
 

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Tharf is my hero :read:
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Yeah 32 is EGR, I replaced mine and still got the code. Turned out it was the little EGR Vacuum Switch. Cost about 15 bucks for a new one.
 

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I CANT SPELL GET OVER IT
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i have a 5.7 350
Yeah, then see my post above. It applies to your truck. Do you know where the EGR valve is located?

And Tunercat :head:

I think I still have it on my laptop.
 

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You need to attach a vacuum pump to the port on the egr valve, if it opens and closes smoothly, then your valve is ok, if it's rough, binds or simply does not move at all - then replace.

Your best bet is just to replace the valve. It's old, and they get bound up with carbon and debris. I'm surprised it's made it this far. It's a commonly replaced part - as the switch is not.

EGR Valve GM P/n's O.E.M. #17087194, 17111851, 17111852

Verify what's on yours.

More info here
 

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Discussion Starter #12
well somebody told me that it was probably the map sensor that needed to be replaced, i know my truck is 16 years old but it only has 75k on it and it runs great, i just want that stupid light off in my dash and maybe get a little better gas mileage, although i'm runnin 35's so it probably wouldn't matter.
 
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