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I have a 1998 that keep giving me a a stupid p401 code- there is a new egr -egr tube to the manifoid. I just took a guy who has a emission shop and it keeps on saying its not ready to do the test. and then I get the code. Any ideas??
 

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Mr. SQ
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I have a 1998 that keep giving me a a stupid p401 code- there is a new egr -egr tube to the manifoid. I just took a guy who has a emission shop and it keeps on saying its not ready to do the test. and then I get the code. Any ideas??
I highly doubt you have a 2.8L from 1998
 

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86' S-10
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A stuck open thermostat most likely. If that is not it, the only other thing I can think of is a bad coolant temperature sensor...

HTH...
 

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It was the coolant temp sensor. I figure it wasn't the thermostat, because the temp would go up and down while driving which means the thermostat was opening and closing. This $11 sensor was causing random high idles, and hard starts when warm but sitting for enough time to run into and out of a store.
 

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86' S-10
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Good job figuring it out :)
 

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Thanks. What is weird though, is I cleared the code, and my truck runs so much better, like no real problems better, yet I am still getting the same code. I wonder if someone installed a different temp thermostat, and it is causing the problem. I will probably change it out on Memorial day just in case.
 

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There are many auto repair shops and auto parts stores that offer a Free Check Engine Light Check or Free Check Engine Light Diagnosis. I personally don't view these offers as scams, but see them more like an opportunity. What these auto facilities will do for free is pull the Check Engine Light Code from the computer in your car. What they will not do is diagnose the problem with your vehicle. When a code is pulled from your car's computer, it gives a pretty general idea of what the problem is. The purpose of this code is the give a technician or a mechanic a place to start with their diagnosis. This helps prevent just guessing, and ultimately replacing parts that don't need to be replaced.
 

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lonemeno
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i have a 42 est how would i go around fixing that i did some timeing when i have the plug under the dash unplugged and set the timing to ten re plugged i drove around and the code came on
 

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4x4 v6 blazer
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Discussion Starter #30
Clear the code and see if it comes back. If it does its the black square thing on the firewall above the dizzy (est) you have to replace. Sometimes when you redo the timing it will still trigger a code for that even if its fine.
 

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lonemeno
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i messed with the wires before work and then turned on the truck and it never came back on since but i know for a fact ever thing was connected so it was one of those freak kind of things
 

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I am trying to figure out a bad running s-10 blazer 2.8 TBI When I short across the terminals A and B on OBD plug I get no response from CEL it just stays on the whole time no flashing. Is it possible that ECM is bad even though the engine runs (very badly I might add)
 

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go buy a $30 reader, stop with a paper clips. you will be a hero on your block once you own one. But the code is the start of the problem it will not tell you what part to change out it will only tell you what sensor is out of range.

 

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I am trying to figure out a bad running s-10 blazer 2.8 TBI When I short across the terminals A and B on OBD plug I get no response from CEL it just stays on the whole time no flashing. Is it possible that ECM is bad even though the engine runs (very badly I might add)
can anyone answer this? I have a 92 2.5 and just jumpered the codes using a piece of electrical wire but will try a paperclip next. SES light comes on and stays on during test. No flashes
 
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