disconnected egr with check engine light on

Discussion in 'Trucks [ Eighteen Wheelers ]' started by 07 pete, Jun 7, 2010.

  1. 07 pete

    07 pete Bobtail Member

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    I was driving today thinking about how to get the cel light to go off. I took an extra pig tail out of my side box put a bulb in it and part of my theory was right I stuck the wires in the unplugged portion of the egr and guess what? the light came on but the cel light stayed on. My theory was the plug didn't know wheather it was turning on the egr motor or the light. so I am thinking it must be a sensor also after the egr cooler so If anyone can build on my way of thinking and get the cel light to go off I'll be watching this post for insight.
     
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  2. diesel07

    diesel07 Bobtail Member

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    It is either detecting an electrical problem or a mechanical problem. Depending on what the code is, it is looking for something different. If its the unplugged electrical connector, then it has to see something that puts the same resistance as the EGR valve. But if its for a mechanical fault code, (low egr flow, etc) its probably looking for a certain amount of EGR elsewhere in the engine which is looking at the EGR valve when the engine is running. not something you can just block off, plug, etc.
     
  3. Gears

    Gears Trucker Forum STAFF - Gone, But Not Forgotten.

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    My CEL came on too. I left the key in the on position while unplugging the EGR. This morning I plugged it back in and the light went off. I'll try unplugging the EGR after turning the key off after 30 seconds or so to see if that makes a difference. Maybe that red wire next the cable that gets unplugged should be unplugged too?
     
  4. NRG

    NRG Light Load Member

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    It should throw an "active" electrical fault code, not a CEL. Since there is an interrupted sensor connection. I did 10k miles so far with EGR off... (unplugged and tapped the 6 o`clock sensor with the key `on` for 15 sec.) so far so good. Water temps are definitely down and getting 7.5 mpg avarage at 65-70mph with 77k gross climbing west coast. :biggrin_25514:
     
  5. belltransit

    belltransit Light Load Member

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    the best way to turn off the light??? pull the bulb!!!
     
  6. ChromeDome

    ChromeDome Road Train Member

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    The best way would be to find out what electrical resistance the EGR valve is giving when hooked up, and then making a resistor plug to put on the wire. This will fool the system into thinking that the valve is still hooked up.
     
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  7. mrdevildog

    mrdevildog Light Load Member

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    the light is not going to go off, the ecm sends out voltage to open and close the valve. also it sends out voltage to a position sensor mounted on the side of the egr, it knows what the flow is because of a pressure sensor the is mounted down stream in the egr crossover pipe. to make a long story short the ecm is smart enough to know whats going on with the system, it was designed/programed that way, if you unplug a connector it will know because it does self diagnostics, its a nice theory but the only way to keep the bulb off is to pull the light bulb or run the engine the way it was designed for. even if you make a resistor or something to put in the connector, the ecm is going to know about it and set other fault codes which in turn will turn on the check engine light.
     
  8. JohnP3

    JohnP3 Road Train Member

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    Could not have said it better my self.
     
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