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1995 Buick LeSabre the issue with this
car is it has an easier trouble code
it's a pee 1406 and this is a linear
type EGR it's a digital valve there's no
vacuum controls to it
and it's this guy here on the screen so
it's five wire the two outer wires are
for the solenoid the three middle wires
are a potentiometer or the valve
position get to a quick shot on the scan
tool of the code and the code we're
going after is this P 1406 so the next
thing I like to do after trouble code is
let's take a look at the data that's on
this and we're going to go back to our
data display and I have this set up
previously so it should still pop up the
way I how to configure and it is and our
focus is on three main data pits and
those three pins would be EGR position
percentage bottom left each of our
position sorry this is desired desired
EGR percentage on the left this EGR
position percentage top right and then
EGR valve position voltage this
percentage is based off this voltage
right away we see a problem this voltage
should be around a half a volt under one
volt say between a half volt one volt
with closed valve we've done a few of
these in the past I think they were like
point six point seven maybe closed valve
position so we have an issue here right
away the next thing I'd like to do with
these depending on the year is to buy
directly control the valve or command
the valve to open unfortunately on this
year I can't do it the only thing I have
available to me is data display my codes
and then clear codes go back again and I
just have my troubleshooter so no
functional tests on this year at all so
we have to manually energize this valve
to open it so we're going to do that
we're going to open the valve and we're
going to watch our position sensor
voltage on the scan tool when we do it
so
let's go back to our data
and got to read customize this
don't really need the RPM in there but
we'll throw it in there anyway those
four pigs and before we do the test let
me get you down on the valve and we'll
talk about the solenoid all right so
what I'm going to do is I'm going to
back probe this connector get off of
this Auto range my two outer wires are
the solenoid control the three middle
wires are for the potentiometer before
we manually energize this valve we need
to know if it's power our ground side
switched we can use a diagram in this
case we're going to use a voltmeter I
have this information section three in
my book transistor drivers output
solenoids so this would be a real good
review for that and first thing I'm
going to do is back probe this pink wire
and block that we got 12 volts showing
on the voltmeter on that wire come out
here to the outer wire so I'm on the two
ends and I have 12 volts on that wire
too so first thing we know is it is
ground side switched second thing would
be how do you know which one is the
ground controlled ground which one's the
feed is real simple gun plug it so
unfuck the the solenoid connector and
you see that that outer wire dropped to
basically zero volts plug it back in and
it jumps up to 12 that is my control
wire I can safely ground that circuit
now something else that's pretty cool
that I don't know if I've shown before
know how to use your meter know how to
use your equipment this is a controlled
ground I can give it a ground through my
meter by very simply switching my red
lead over to my aunt port I'm already
connected to ground and so what we will
have is a jumper wire and ammeter is
nothing more than a jumper wire with a
gauge on it
so switch this two amps we don't need
the amperage reading but we can show it
to move this over see if the camera
picks up that click
and so on and off so that's energized
right now we got a reading of around 1.3
amps that solenoid is energized right
now and over on the scan tool real quick
notice that my position voltage did not
change it's staying at zero so now is
that valve opening we hear it click is
it actually opening there's a nice test
for that
come back to the car
what we'll do is we'll redo this test
I'm going to take this out of the ant
port close the valve zero amps we're
going to start the car and when I
energize this of course you pretty much
get rough install telling me the valve
actually open good start it
so I'm giving this solenoid aground
through my ammeter
shut it off so what that test told me
not only is the clicking that we heard
good telling me we have control but that
yes in fact that valve is opening by the
fact that this thing got real real raw
our focus now goes toward this position
sensor don't forget to take your lead
back out of the amp port go back to
voltage anytime you're done doing
testing over here you have to regardless
of what you do up here if you leave that
over there you still have a jumper wire
in your hand so be careful with go back
to DC volts I'm gonna go my middle wire
which is my position sensor signal wire
and we want to have the key on for this
test remember we're at zero votes on the
scan tool for this
and you see we're reading zero volts on
the voltmeter - on this signal wire so a
lot of people at this point would put an
EGR valve in this you have zero volts on
a signal wire let's throw a valve in it
in fact a lot of people based on the
trouble code with their own EGR valve in
this so this next part will be a real
good review for section 7 in my book
which is potentiometers and that's what
we're dealing with here a potentiometer
has a 5 volt ref a signal on the ground
I'm on the signal wire we have 0 volts
here all the time next thing you have to
do when you have no signal is check your
reference check your ground check for
opens and shorts in the signal circuit
next step we're going to check the
reference so all I'm going to do is move
my my lead down I have a gray wire here
a black wire here in the middle gray
wire is my reference black wires my
ground I'll start with the ground have 0
volts on that ground that's a good
ground less than 100 millivolts is what
we want
next thing check the reference circuit
and now we have a problem
this reference should be 5 volts and I'm
reading 0.06 so this is what's causing
this trouble code no reference voltage
you're not going to have a signal we
don't need an EGR valve we have a wiring
problem so the car runs this is a 5 volt
reference we've done other other videos
that deal with no 5 volt reference where
a car doesn't run shorted reference
circuit not the case here this car runs
it's real easy to figure out if the
circuit sorted by the simple fact the
car runs and then another one would be
to check another sensor that uses the 5
volt reference so there's another gray
wire on the TPS I'm going to go right to
that which is right next to it it's
right here and we're going to back probe
this TPS circuit and you can see on my
meter I have 5 volts on my TPS so my
reference circuit isn't shorted what
we're dealing with is an open to this
EVP signal EGR valve position sensor
signal we have an open on this 5 volt
reference line going to the valve it's
not a short to ground because the short
the ground would pull everything down so
before we start attacking this harness
and pulling everything apart our next
step is to check that same reference
wire in another location at another
sensor or at the computer so we need a
wiring diagram now
okay here's my EGR valve in this diagram
this gray wire right here is my
reference goes to the next page so it
just comes down there's no splices goes
to the next page it's right here so it
comes over this way down here right to
the computer and it says 5-volt
ref there are no splices in that leg of
this five volt reference circuit now we
know for a fact that this 5 volt ref
goes to other circuits we know for sure
the TPS is on it you would think by
looking at the diagram that there's only
one circuit using this 5 volt reference
but that's not the case for some other
videos just type in 5 volt reference
circuit under my username and I have a
at least 3 or 4 other videos that deal
with a reference circuit and how they're
actually shared internally and you know
what looks like a single circuit is not
or in this case we look at the other
part of the diagram and we see another
five volt raff it looks like 2 separate
5 volt reference circuits it's not it's
the same but what's nice to know for us
for this step is there are no other
shared circuits so what I don't want to
do is pull this whole harness apart I
want to go at the computer now take a
measurement here if I read 5 at this
location right here and we read 0 at our
EGR here showed you guys that one
already if we read 0 here and we read 5
here then we have an opening harness
again we're not worried about a sort to
ground because of symptoms and the fact
that my TPS has 5 if I read 0 at the
computer then we have a computer problem
it's that simple
so we're going to the computer next
doing a voltage measurement right there
ok we've already identified the pin on
the computer and I have it back probed
it's a gray wire here this is our
reference to our EGR get you a reading
on the voltmeter we see our same 0 volt
signal
our reference is zero at the computer it
is also zero at the EGR valve again
we're not worried about a short to
ground here guys because if this wire
was shorted to ground it would pull the
entire 5 volt reference to ground not
the case so what we have what this is
looking like is a bad computer let's get
a shot at the other 5 volt reference ok
this is my other 5 volt reference
circuit this goes to the TPS and I
didn't see on the diagram that it went
anywhere else so I'm just gonna rest
this against the T pin if I can and get
a voltage reading on this circuit now we
already checked it externally I just
want you guys to see that and take you
up to the meter
and there you go your 5 volts to your
TPS is good further confirming again
that we don't have a short to ground on
the EVP 5 volt reference circuit because
if we did it would pull this one down
too there are not two separate 5 volt
reference circuits there's only one I
know externally it looks like there's
two there's not it's one circuit so
really at this point we only have one
other option and that'd be a spread
apart pin on the computer connector on
this EVP circuit it's either going to be
that or it's a bad computer so we'll
check the pin real quick alright so
we're going to check this pin and I've
had some real good questions on this and
I've mentioned how to do it I'm going to
show it I think this is the probably the
first time I've shown this but you can
see the the gray wire that that I have
back probed its if you count the pins
it's actually 1 2 3 4 5 6 7 down from
the top and so we flip this over
all new America
it's these inside holes right here not
the outside
so it'd be seven down so it's one two
three four five six seven so it's that
pin right there that that's the one we
want to worry about in fact I'm going to
mark that real quick with my pen
so it's that one right there
Macallan again
yep all right so that's the that's the
one in question is that is there a
potential that that pin is spread apart
in there you definitely can't see it you
can't do a visual so what we want to use
is this is made by this company one of
you guys asked me recently where I get
these I don't know I get them from our
tool room here at the school so I'm not
sure where they get them but that's the
company that makes it what these are is
us is tortes tip cleaners and what they
have is is different size different size
cleaning tips and so they're all gauged
differently and what I want to do is I
want to find a gauge or a cleaning tip
that has a small amount of drag on these
pins and I want to do it not on the one
we're worried about I want to gauge it
to one of my other ones that I know are
not a problem so I'm going to try to do
that keep my arms out of the way while
I'm doing this difficult I'm looking for
one again that has some drag to it
and I'm just going to pick one I'm
guessing here and I'm going to gauge it
off of one of these other ones not the
one that we're worried about that one's
actually pretty good that first try so I
can feel some slight drag on that pin I
can check one of the other ones I'm not
forcing this in any way shape or form
I'm just feeling the pin drag in fact
you can hear that and I'll come up here
and and that's the right one I want to
use now this would be the gauge to check
for a pin drag and I'm going to check
this one right here the one for our EGR
and I don't know if the camera is
picking that up
same exact pin drag as these other ones
so what we know now for a fact is that
we don't have a spread pin that would be
the final variable here before we call
this engine computer this needs an
engine computer such thing is these GM
computers they go bad all the time the
older ones and so I'm not really that
concerned about it in fact this guy
changed this computers what he told me a
few months ago for a stalling problem
which was pretty typical
so what we have inside of this board is
somewhere between the five volt
regulator and these two circuits that
come out is we have an open in this
board and you know what I can do for the
rest of this video because I don't have
another computer right now is I'm going
to jump this five volt reference over
here which is good to this five volt
reference over here which is bad and
shoot the rest of the video to show you
what this EVP signal looks like with a
good reference so jumper wire I'm just
going to take and you know you could
probably do this permanently if you
wanted to you could take this gray wire
here which is a reference us take the
insulation off of it a little bit same
thing here run a jumper between solder
it tape it up this is inside the car I
really wouldn't have a problem with that
fix you know if this guy wants to
do that that's going to be up to him it
needs a computer jump these two together
being fully confident what I'm doing and
I'm going to turn the key on will go
back under the hood and redo our techs
quick comment on this pin drag test I
just showed you guys some of you might
be thinking this is overkill but hey
when it comes to callin a $1,300
computer not that this car is this one's
about a hundred bucks these go bad all
the time but think about it you got a
$1,300 computer you're ready to call is
being bad do you want to check pin drag
to make sure I would think so so it's an
important process you need to know how
to do it okay we have the key on right
now and I'm back on my EVP signal wire
with the multimeter that's the middle
wire on this five pin EGR valve I'm
reading 0.85 of a volt that's what we
want to see when it comes to these on
the scan tool you see the same number
we're reading 0.8 of a volt over here
and what I can do is I'll energize EGR
valve show you this signal over here I'm
just going to use my ammeter again and
just to be clear about what I'm doing
for that think about it we're using a
voltmeter already your voltmeter ground
so over here on the battery voltmeter
positive is on the signal what I want to
do is be the ground for the solenoid so
move this over to the solenoid wire and
you see we're reading 12 volts and
knowing your meter just taking this lead
over here taking it away from that very
very high resistance that's in the
voltmeter
moving it to the ammeter and no reading
up here still on voltage doesn't matter
I just connected this to ground it
clicked you want a reading of amperage
you can move it over
reading 1.2 4 amps very high current
solenoid get you a shot back on the scan
tool and you'll see that my EVP signal
is a 4.7 volts take this off
watch the valve closed point 8 energize
it again watch the valve open that is a
confirmed fix when we replace this
computer or if we do a jumper and then
do it that way this car is going to be
fixed alright so a quick recap of what
we've done here we did a nice review on
a GM 5 pin linear EGR also known as a
digital EGR valve or now I think the
digital ones I'm sorry I'm using the
wrong terminology the digital ones were
the three solenoid ones this is a single
solenoid they call this a linear EGR
very commonly used valve chrysler honda
GM they all use a version of it testing
is very similar although be careful with
your polarity some of the newer ones
will power side switch them instead of
ground side switched don't just get in
there and start jumping things to ground
unless you absolutely know what you're
doing I showed you a way to identify
that with a voltmeter for more info on
that that's section 3 refer to it don't
do this kind of procedure unless you
absolutely know the polarity of that
solenoid so this one was ground side
switched nice review of how to identify
that with a voltmeter nice review of a
potentiometer being a three wire sensor
needs a reference ground in a signal to
function properly we are missing our
reference and we also showed in here how
to
to a pin drag test on the computer and a
nice review of that whole five volt
reference circuit so I think this was a
really good one not just don't look at
this as a 95 Buick and how many of these
are you going to see look at this as a
fundamental and these procedures that
we've shown here apply to everything so
again the fix here is going to be a
wreath of replace the engine computer or
at least dump those two wires together
and and fix it that way I really
wouldn't have a problem with it because
really that's what it's doing inside of
the computer
faulty leg of the five volt reference
circuit
you
