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Discussion Starter #1
My truck is throwing a DTC 45 - EGR Vent Error.

I replaced the EGR valve and MAP sensor 2 weeks ago with new ones. Been driving great ever since til' 2 days ago. It threw the code and I cleared it and cleaned all known battery contacts and and grounds. It still throws the code.

What is an EGR vent and where is it located and how the heck do I fix it?

Thanks!
 

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Not zactly sure how EGR is configured on OBD-I (still waiting on my donated set of OBD-I manuals to arrive for the reference library) but if it works like OBD II (see schematic in photo gallery FAQ sticky toward the end), 3 solenoids involved to the S trucks system, WG, EGR, & EGR vent

WG opens/closes the WG; EGR supplies vac when required open EGR valve, then the EGR vent acts as a regulator to bleed vac to modulate open or close as required to make PMC happy, in OBDII 96+ years the firewall baro monitors this vac to tell PCM position of EGR, which is why OBDII just can't plug EGR valve to bypass them, differences of flow monitored thru firewall baro will code if not correct.

Maybe one of the OBDI guys can add to the how it works piece, 1st I'd run full vac checks from pump to solenoids to make sure you don't have problem there, then double check vac lines as they age the nylon lines can develop cracks hard to detect. A functioning vac pump at the pump will have 17-25 " vac, inlet of solenoids should be same, outlet of functioning solenoids will vary as PCM pulses them, you will have to monitor those while driving and gauge in the cab.

Get a simple press/vac test gauge (mandantory test equipment IMO especially for S vin trucks) about $18 or so in auto part store then also get a long piece of 1/8" rubber vac hose hose long enough to make it from engine compt into cab then you can drive and check various devices on engine, but remember to not pinch hose closed as you will "deadhead" flow and get incorrect readings.
 

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In order to get DTC 45 you have to have either a broken wire at the EGR VENT solenoid, or the solenoid itself has an open coil. Carefully check the wire from the solenoid plug all the way back to where it meets the main wiring harness. The wires to the solenoids tend to break the conductors while leaving the insulation intact. Easiest way to find a break is to start the engine and gently work your way down the wires wiggling as you go. If the idle stumbles, you have found the broken wire.


I am sitting in the Denver airport but I will be home in a few hours if you need a picture.
 

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Hey John does OBDI work like OBDII, I just don't know, also does firewall baro come into play like in OBDII
 

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Yes the baro comes into play but that just monitors the 31-33 DTC's. The actual circuit being open or shorted sets 45.

Well, it works that way till ya stick the Maxi-TorK in her :ro)
 

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Discussion Starter #6
I am sitting in the Denver airport but I will be home in a few hours if you need a picture.
I could sure use a pic...but since your in denver you could just stop by my house....it's only about 5 hrs away:lol:

I'll keep an eye out for the pic. Thanks for your help. I have no idea where you talking about. I know where the egr valve is and map sensor are but other than that i have no idea about this egr stuff.
 

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Stay tuned grasshopper, all will be revealed, 6.5s aren't a big mystery, I just got off phone with NVMNTLION says OBDI is similar to OBDII so pics in FAQ sticky will work for you, control logic is a little different but not much.
 

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Discussion Starter #8
Well I checked the plugs. All 3 have been replaced/spliced at some point. I wiggled all 3 individualy and nothing happened.

Is it going to cause problems (other than showing a code now and then) or can I just kinda ignore that code and drive on?

Thanks
 

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From little I've read a long time ago about OBD-I systems, are they are great to bypass all the EGR stuff, as compared to the OBD-II systems.

Sounds logical about open circuit on the coil....
 
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